subject:"Re\: STEP 3"

> On 15 Aug 2019, at 13:28, Bruce Kellett  wrote:
> 
> On Thu, Aug 15, 2019 at 7:49 PM Bruno Marchal  > wrote:
> On 15 Aug 2019, at 02:54, Bruce Kellett  > wrote:
>> On Wed, Aug 14, 2019 at 10:10 PM Bruno Marchal > > wrote:
>> On 12 Aug 2019, at 14:42, Bruce Kellett > > wrote:
>>> 
>>> That is simply incorrect. I refer you again to Zurek, who works in a 
>>> basically Everettian framework, but he stresses the importance of 
>>> environmental induced superselection (einselection) in producing the 
>>> preferred pointer basis. This then breaks things, in the sense that no 
>>> other basis is stable against decoherence, and other sets of basis vectors 
>>> rapidly (in times of the order of femtoseconds) collapse on to the 
>>> preferred pointer states. This is the basis of the emergence of the 
>>> classical world from the quantum substrate. And this occurs in Everett's 
>>> relative state approach just as much as in a Copenhagen-like collapse 
>>> models.
>> 
>> That explains why the many histories will look classical. But if I observe a 
>> cat in the dead+alive state,
>> 
>> The point of the existence of a preferred basis is that you will never 
>> observe a cat in a "dead+alive" state.
> 
> If that is what you mean, we both agree that Everett + Zurek solves that 
> problem. But the point is that If I observe the cat with an apparatus 
> deciding between alive and dead, I will put myself in the corresponding 
> superposition, unless some physical collapse occurs, but then we are no more 
> in Everett’s QM (QM without collapse).
> 
> No, you do not see any superposition.

Yes. We agree on this. The point is that I will not see it, because I am part 
of it, nor because it would have disappeared in some way.

> The cat itself is never in a superposition because decoherence brings about a 
> definite live state or dead state.

So we do disagree, at least if you claim that the superposition state disappear 
and QM applies to the cat. 

If there is no wave collapse, saying that some unknown particle interacting 
with the cat demolished the superposition state means only that the particle 
has been entangled with the state of the cat, and that being unable to track 
that particle makes me unable to handle the superposition anymore, but this 
means that the cat remains superposed, the particle get also superposed, and my 
whole environment get superposed. By the double QM linearity, the superposition 
never disappeared at all. The cat + the particle + me + the universe evolved 
through a unitary rotation where I am locally described in the two terms of the 
wave: seeing the cat alive and seeing the cat dead.

Decoherence in Everett (entanglement), and in Zurek (at least the perhaps old 
paper I read) does not make the “other branches vanishing”, it makes just my 
alternate history inaccessible.

> By the time you open the box, you have also split according to the classical 
> basis,

Ah, but that was my point. 

> so your probability of seeing a live or dead cat is just the classical 
> ignorance probability.

Yes, like the H guy in Moscow and in Washington, already duplicated, but before 
they open the door of the reconstitution box (in the 2 cities). The H-guy is 
ignorant on which branch of the computation he/she belongs.

> Opening the box does not collapse anything.

Thanks for reassuring me. That was my point.

> The point is that even if there is some superposition, it lasts no more than 
> a few nanoseconds.

That is misleading, as some people will interpret this by a collapse. I am 
happy you reject that interpretation. I agree that, even we’ll before I open 
the box, I have already been multiplied, unless some engineer trick to isolate 
the cat completely, which is just impossible today.

> After that time, your position is one of classical ignorance -- you are 
> either in the branch with the live cat, or the branch with the dead cat.

Yes, like after the WM-duplication, I am either in Moscow or in Washington. 
Pure classical ignorance.

> Opening the box does not change your relative state, or collapse anything.

Exactly my point. 

> There is no "you" that is in a superposition of these branches (just as there 
> is no "you" that is in both Washington and Moscow in step 3).

Exactly. In the first person perspective. Obviously, the 3p observer which 
looks at the entire setup can see me in both cities.
The only difference with the superposition, is that the 3p-view is technically 
lost from the experimental local (first person plural) view.

> So it is just like someone tossing a classical coin that you can't see.

Yes.

We do agree! (I hope you agree with this).

Then with mechanism, we have a generalisation of the relative state approach, 
by taking all computations into account, a concept which makes sense through 
Church-Thesis, and if you accept that thesis, all

Re: STEP 3

2019-08-15 Thread Bruce Kellett

On Thu, Aug 15, 2019 at 7:49 PM Bruno Marchal  wrote:

> On 15 Aug 2019, at 02:54, Bruce Kellett  wrote:
>
> On Wed, Aug 14, 2019 at 10:10 PM Bruno Marchal  wrote:
>
>> On 12 Aug 2019, at 14:42, Bruce Kellett  wrote:
>>
>>
>> That is simply incorrect. I refer you again to Zurek, who works in a
>> basically Everettian framework, but he stresses the importance of
>> environmental induced superselection (einselection) in producing the
>> preferred pointer basis. This then breaks things, in the sense that no
>> other basis is stable against decoherence, and other sets of basis vectors
>> rapidly (in times of the order of femtoseconds) collapse on to the
>> preferred pointer states. This is the basis of the emergence of the
>> classical world from the quantum substrate. And this occurs in Everett's
>> relative state approach just as much as in a Copenhagen-like collapse
>> models.
>>
>>
>> That explains why the many histories will look classical. But if I
>> observe a cat in the dead+alive state,
>>
>
> The point of the existence of a preferred basis is that you will never
> observe a cat in a "dead+alive" state.
>
>
> If that is what you mean, we both agree that Everett + Zurek solves that
> problem. But the point is that If I observe the cat with an apparatus
> deciding between alive and dead, I will put myself in the corresponding
> superposition, unless some physical collapse occurs, but then we are no
> more in Everett’s QM (QM without collapse).
>

No, you do not see any superposition. The cat itself is never in a
superposition because decoherence brings about a definite live state or
dead state. By the time you open the box, you have also split according to
the classical basis, so your probability of seeing a live or dead cat is
just the classical ignorance probability. Opening the box does not collapse
anything. The point is that even if there is some superposition, it lasts
no more than a few nanoseconds. After that time, your position is one of
classical ignorance -- you are either in the branch with the live cat, or
the branch with the dead cat. Opening the box does not change your relative
state, or collapse anything. There is no "you" that is in a superposition
of these branches (just as there is no "you" that is in both Washington and
Moscow in step 3). So it is just like someone tossing a classical coin that
you can't see.

Bruce

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Re: STEP 3


> On 15 Aug 2019, at 02:54, Bruce Kellett  wrote:
> 
> On Wed, Aug 14, 2019 at 10:10 PM Bruno Marchal  > wrote:
> On 12 Aug 2019, at 14:42, Bruce Kellett  > wrote:
>> 
>> That is simply incorrect. I refer you again to Zurek, who works in a 
>> basically Everettian framework, but he stresses the importance of 
>> environmental induced superselection (einselection) in producing the 
>> preferred pointer basis. This then breaks things, in the sense that no other 
>> basis is stable against decoherence, and other sets of basis vectors rapidly 
>> (in times of the order of femtoseconds) collapse on to the preferred pointer 
>> states. This is the basis of the emergence of the classical world from the 
>> quantum substrate. And this occurs in Everett's relative state approach just 
>> as much as in a Copenhagen-like collapse models.
> 
> That explains why the many histories will look classical. But if I observe a 
> cat in the dead+alive state,
> 
> The point of the existence of a preferred basis is that you will never 
> observe a cat in a "dead+alive" state.

If that is what you mean, we both agree that Everett + Zurek solves that 
problem. But the point is that If I observe the cat with an apparatus deciding 
between alive and dead, I will put myself in the corresponding superposition, 
unless some physical collapse occurs, but then we are no more in Everett’s QM 
(QM without collapse).

Bruno




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Re: STEP 3


> On 13 Aug 2019, at 18:37, Jason Resch  wrote:
> 
> 
> 
> On Tuesday, August 13, 2019, John Clark  > wrote:
> On Wed, Aug 7, 2019 at 9:40 AM Bruno Marchal  > wrote:
> 
> On 7 Aug 2019, at 15:08, Bruce Kellett  > wrote:
>  
> >> What exactly is the difference between something that it is impossible in 
> >> principle to detect and something that does not exist?
>  
> > It is like the difference between the human existence and the human non 
> > existence, for an alien situated in a very far away galaxy. The fact that 
> > this alien cannot detect us does not make the human disappearing. 
> 
> You're dodging the question. We can certainly detect ourselves, and it is not 
> impossible in principle for a alien in a distant galaxy to detect us, and 
> that is very different from your silly phantom computations that pure numbers 
> are suposed to be able to perform. 
> 
> > It is like the other side of the moon before we built rocket. 
> 
> Nobody ever said there was a philosophical problem in observing the far side 
> of the moon, it was always just a matter of engineering, but no amount of 
> engineering can make your ridiculous phantom calculations real. If they 
> existed it would be possible in principle to count the number of angels that 
> were sitting on the head of a pin, but your non-material Turing Machine is 
> hopeless. 
> 
> 
> The conversation was about other branches of the wavefunction.  (Which I 
> think you believe in despite not being able to see, nor them being able to 
> make a CPU useful to you).

Well seen. 

Bruno



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> 
>  
> John K Clark 
> 
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Re: STEP 3

> On 13 Aug 2019, at 16:53, John Clark  wrote:
> 
> Nobody ever said there was a philosophical problem in observing the far side 
> of the moon, it was always just a matter of engineering, but no amount of 
> engineering can make your ridiculous phantom calculations real.

There is a philosophical problem even on milk in the fridge when the fridge is 
close. We can use Einstein’s reality principle, but as you know, this leads to 
other problem, and people different on the existence or not of a collapse. Yes, 
those are not problem if we adopt a FAPP-philosophy.

> If they existed it would be possible in principle to count the number of 
> angels that were sitting on the head of a pin,

With mechanism, that is the same as the problem of how much bits or qubits we 
can process in a volume similar to the head of a pin. It makes sense.

> but your non-material Turing Machine is hopeless. 

Then Church, Turing, Post, Kleene, Gödel and many more are all hopeless, in 
fact elementary arithmetic becomes hopeless.

Bruno

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Re: STEP 3

2019-08-14 Thread smitra


On 15-08-2019 06:25, Bruce Kellett wrote:

On Thu, Aug 15, 2019 at 7:23 AM smitra  wrote:


On 14-08-2019 00:44, Bruce Kellett wrote:


You over-elaborate a simple schematic. My A(x) and B(x) are

simply the

amplitudes of the wave function at point x on the screen from the

two

slits. To get the intensity at x, you add the amplitudes and take

the

modulus squared -- you do not add the intensities from each slit
separately.


What matters is that you can get interference of the orthogonal
components in the superposition. Whether or not you do actually get

interference is not orthogonality before measurement, but after
measurement. If the photons moving through the slits interact with
another system initially in some state |C> such that if the photon
moves
through slit A the state |C> changes to |D> while it changes to |E>
if
the photon moves through slit B, then the interference pattern will
be
the function Re[A(x)*B(x)], this will become zero if |C> and
|D>
are orthogonal, which means that you still have a superposition of
two
orthogonal terms in the MWI sector where a photon lands on some
specific
spot on the screen. The system then has perfect which-way
information.


I don't think this quite works either. Look at it this way. Take |A>
as the wave function for going through slit A, and |B> the
corresponding wave function for going through slit B. The
superposition (|A> + |B>) is the wave function that propagates to the
screen. At the screen, the intensity is the square of this:
   (A| + |B>)() =  |A|^2 + |B|^2 +  + ,
and there is interference. This is because you have added together the
paths through each slit, but you don't know which slit was traversed,
so A and B are coherent.

If you now add a detector at the slits that registers L (for Left) if
A was traversed, and R (for Right) if B was traversed, the original
superposition becomes
   (|A>|L> + |B>|R>)
because the detector becomes entangled with the slit through which the
photon went. If we now go to the intensity at the screen, we obviously
get
   |A|^2 + |B|^2 +  + 
The detector states recording L or R for which slit the photon
traversed are orthogonal,  =  = 0, so  detecting which slit
the photon went through destroys the interference. If there is no
detection at the slits, the amplitudes are coherent, they are not
orthogonal, and there is interference.



 = 0 due to orthogonality (and this is preserved as the screen is 
approached as the state evolves in a unitary way), what we measure at 
the screen is  +  as a function of the position x on 
the screen. If we add up all the counts on the screens from all 
positions then the interference effect averages out to zero due to 
orthogonality, but that doesn't matter. We can still see fringes and 
peaks on the screen.


Saibal

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Re: STEP 3

2019-08-14 Thread Bruce Kellett

On Thu, Aug 15, 2019 at 7:23 AM smitra  wrote:

> On 14-08-2019 00:44, Bruce Kellett wrote:
> >
> > You over-elaborate a simple schematic. My A(x) and B(x) are simply the
> > amplitudes of the wave function at point x on the screen from the two
> > slits. To get the intensity at x, you add the amplitudes and take the
> > modulus squared -- you do not add the intensities from each slit
> > separately.
>
>
> What matters is that you can get interference of the orthogonal
> components in the superposition. Whether or not you do actually get
> interference is not orthogonality before measurement, but after
> measurement. If the photons moving through the slits interact with
> another system initially in some state |C> such that if the photon moves
> through slit A the state |C> changes to |D> while it changes to |E> if
> the photon moves through slit B, then the interference pattern will be
> the function Re[A(x)*B(x)], this will become zero if |C> and |D>
> are orthogonal, which means that you still have a superposition of two
> orthogonal terms in the MWI sector where a photon lands on some specific
> spot on the screen. The system then has perfect which-way information.
>

I don't think this quite works either. Look at it this way. Take |A> as the
wave function for going through slit A, and |B> the corresponding wave
function for going through slit B. The superposition (|A> + |B>) is the
wave function that propagates to the screen. At the screen, the intensity
is the square of this:
   (A| + |B>)() =  |A|^2 + |B|^2 +  + ,
and there is interference. This is because you have added together the
paths through each slit, but you don't know which slit was traversed, so A
and B are coherent.

If you now add a detector at the slits that registers L (for Left) if A was
traversed, and R (for Right) if B was traversed, the original superposition
becomes
   (|A>|L> + |B>|R>)
because the detector becomes entangled with the slit through which the
photon went. If we now go to the intensity at the screen, we obviously get
   |A|^2 + |B|^2 +  + 
The detector states recording L or R for which slit the photon traversed
are orthogonal,  =  = 0, so  detecting which slit the photon went
through destroys the interference. If there is no detection at the slits,
the amplitudes are coherent, they are not orthogonal, and there is
interference.

Bruce

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Re: STEP 3

2019-08-14 Thread Bruce Kellett

On Wed, Aug 14, 2019 at 10:10 PM Bruno Marchal  wrote:

> On 12 Aug 2019, at 14:42, Bruce Kellett  wrote:
>
>
> That is simply incorrect. I refer you again to Zurek, who works in a
> basically Everettian framework, but he stresses the importance of
> environmental induced superselection (einselection) in producing the
> preferred pointer basis. This then breaks things, in the sense that no
> other basis is stable against decoherence, and other sets of basis vectors
> rapidly (in times of the order of femtoseconds) collapse on to the
> preferred pointer states. This is the basis of the emergence of the
> classical world from the quantum substrate. And this occurs in Everett's
> relative state approach just as much as in a Copenhagen-like collapse
> models.
>
>
> That explains why the many histories will look classical. But if I observe
> a cat in the dead+alive state,
>

The point of the existence of a preferred basis is that you will never
observe a cat in a "dead+alive" state.

Bruce

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Re: STEP 3

2019-08-14 Thread smitra


On 14-08-2019 00:44, Bruce Kellett wrote:

On Wed, Aug 14, 2019 at 8:28 AM smitra  wrote:


On 13-08-2019 13:33, Bruce Kellett wrote:


Of course A(x) and B(x) refer to the same point on the screen.

That is

not a collapse, that is just what the notation means.


A(x) and B(x) considered as the representations of |A> and |B> in
the
position basis, i.e. A(x) =  and B(x) =  are still
orthogonal
states, as they represent the orthogonal states |A> and |B>:

0 =  = Integral over x of d^3x = Integral over x of

A*(x)B(x) d^3x

But you interpret this as the total counts of particles on the
entire
screen not changing which you call an absence of interference.
However
interference is what we detect locally on each point on the screen.
You
can't say that for each point x0 on the screen, A(x0) and B(x0)
are
particle states. These values are not the quantum states of the
particle
before it hits the screen, unless you would have done a measurement

localizing the particle near x0.


The spot on the screen may well be such an experiment.


So, your argument only makes sense if you invoke collapse via a
position
measurement.


You over-elaborate a simple schematic. My A(x) and B(x) are simply the
amplitudes of the wave function at point x on the screen from the two
slits. To get the intensity at x, you add the amplitudes and take the
modulus squared -- you do not add the intensities from each slit
separately.

Perhaps the problem stems from my using the ket vector representation
for single complex numbers. But complex numbers are never orthogonal,
so using the ket generalises this interference result to general state
vectors. Integrating over the screen is not relevant to the intensity
at each point.


What matters is that you can get interference of the orthogonal 
components in the superposition. Whether or not you do actually get 
interference is not orthogonality before measurement, but after 
measurement. If the photons moving through the slits interact with 
another system initially in some state |C> such that if the photon moves 
through slit A the state |C> changes to |D> while it changes to |E> if 
the photon moves through slit B, then the interference pattern will be 
the function Re[A(x)*B(x)], this will become zero if |C> and |D> 
are orthogonal, which means that you still have a superposition of two 
orthogonal terms in the MWI sector where a photon lands on some specific 
spot on the screen. The system then has perfect which-way information.


Saibal

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Re: STEP 3

2019-08-14 Thread Bruno Marchal


> On 12 Aug 2019, at 14:42, Bruce Kellett  wrote:
> 
> On Mon, Aug 12, 2019 at 7:36 PM Bruno Marchal  > wrote:
> On 12 Aug 2019, at 04:06, Bruce Kellett  > wrote:
>> 
>> If you do not measure which slit the photon went through, then the 
>> superposition of slits is not broken by decoherence.
> Decoherence break things only if there is a collapse.
> 
> That is simply incorrect. I refer you again to Zurek, who works in a 
> basically Everettian framework, but he stresses the importance of 
> environmental induced superselection (einselection) in producing the 
> preferred pointer basis. This then breaks things, in the sense that no other 
> basis is stable against decoherence, and other sets of basis vectors rapidly 
> (in times of the order of femtoseconds) collapse on to the preferred pointer 
> states. This is the basis of the emergence of the classical world from the 
> quantum substrate. And this occurs in Everett's relative state approach just 
> as much as in a Copenhagen-like collapse models.

That explains why the many histories will look classical. But if I observe a 
cat in the dead+alive state, some people will still live the two alternative 
quasi-classical histories. 



> 
> Without collapse, even if I measure which slit the photon went through, the 
> two terms of the superposition continue to exist, describing me seeing both 
> outcomes, and both me feel like if there has been a collapse,
> 
> No, that is not really true. Complementarity plays a role. Measurement of 
> which slit the photon went through is incompatible with the effective 
> momentum measurement that gives interference at the screen. That is 
> essentially why the slit measurement destroys the possibility of 
> interference. There is an incompatibility between the measurements -- 
> basically related to the non-commutation of position and momentum operators 
> and the Heisenberg uncertainty principle.

I agree with this, but fail to see why it makes my statement above false.



> 
> and that decoherence is physical real, but that illusion is explained by the 
> formalism, in a manner similar to the WM duplication: it is just first person 
> indeterminacy, not in a self-duplication, but in a self entanglement.
> 
> Not really true, either. Decoherence, the formation of a stable pointer 
> basis, and the like, are all essential for the emergence of the classical 
> from the quantum, and the formation of objective physical states. This is the 
> operation of Zurek's Quantum Darwinism -- the environment acting as witness. 
> So this is third person objective physics -- it is not first person 
> indeterminacy.


Why? The environment, in a world with brains, acts as a witness of all 
quasi-classical histories. Decoherence explains why those histories look very 
classical, but it does not select one classical history (cat alive, say), it 
put itself in a superposition of the (two, here) classical histories. 

Bruno



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Re: STEP 3

2019-08-14 Thread Bruno Marchal


> On 12 Aug 2019, at 14:28, Bruce Kellett  wrote:
> 
> On Mon, Aug 12, 2019 at 7:30 PM Bruno Marchal  > wrote:
> On 11 Aug 2019, at 14:09, Bruce Kellett  > wrote:
> 
>> It is not a matter of the difference between collapse or no-collapse models 
>> -- it is a matter of the basic interpretation of what Everett's "relative 
>> states" actually are, and why the basis problem is so important for Everett.
> 
> Everett makes clear that the choice of the base os irrelevant for the global 
> description,
> 
> Maybe for the global description, but not for recovering the results of 
> experience. Everett got this latter problem wrong (he probably wasn't even 
> aware that there was a problem.).

That is not my feeling, but I will take a look back to what Everett said in his 
long text.




> Zurek says:
> "The basis ambiguity is not limited to pointers of measuring devices. One can 
> show that also very large systems (such as satellites or planets) can evolve 
> into very non-classical superpositions.

I agree (with Zurek).



> In reality, this does not seem to happen.

OK.



> So there is something that picks out certain preferred quantum states, and 
> makes them effectively classical.

… relatively to the observer. The observer is itself the result of many 
interaction/measurement which picked the base defining its computational 
properties.




> Before there is collapse, a set of preferred states, one of which is selected 
> by the collapse must somehow be chosen.

OK, with “apparent collapse” instead of “collapse”. The context should be given 
if this is what Zurek means. Some texts by Zurek explicitly rejects the idea 
that the collapse is a physical event (like in Everett).




> There is nothing in the writings of Everett that would hint at such a 
> criterion for such preferred states, and nothing to hint that he was aware of 
> this question The preferred basis problem was settled by environment 
> induced superselection (einselection), usually discussed along with 
> decoherence.


OK. And this explains the appearance of quasi classical histories.



> When environmental monitoring is focussed on a specific observable of the 
> system, its eigenstates form a pointer basis:


Yes. This is how the “brain” has been able to evolve, and why the position 
observable plays a key role for macroscopic entities.




> They entangle least with the environment (and, therefore, are least perturbed 
> by it.) This resolves the basic ambiguity." (Zurek, arxiv:0707.2832 July 2007)

OK.



> 
> Zurek goes on to develop this at some length, but the basic point is 
> stability under environmental interactions, so the permanent, objective 
> records of the result can be formed in the environment. This is the basis of 
> intersubjective agreement about the result,

Yes, it provides a notion of first person plural sharable observation.



> namely, objectivity. Quantum Darwinism means that the results that we observe 
> are classically stable.
> 
> and the choice of the base is done by the observer for the local description,
> 
> The observer does not chose the basis -- he might choose what to measure, but 
> it is the environment that ultimately decides what bases is stable, and which 
> other bases rapidly collapse on to states in the pointer basis.

OK. My way to express this was perhaps unclear. It is evolution which has 
“chosen” the base, somehow.




>  
> exactly like with digital mechanism, where the notion of universal numbers 
> play the role of the base. The whole theology and physics does not depend on 
> the choice of the universal machinery we posit at the start, but from the 
> points if view of each relative universal numbers, such difference play a key 
> role in the local happenings and predictions.
> 
> This is no longer quantum mechanics, nor has it anything to do with physics.

Only because you work in the materialist and non mechanist frame, I guess. With 
mechanism, those becomes key element in the explanation of why and how a 
physical reality appears and get sharable by many independent universal 
machines. 

Bruno



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Re: STEP 3

2019-08-13 Thread Bruce Kellett

On Wed, Aug 14, 2019 at 8:28 AM smitra  wrote:

> On 13-08-2019 13:33, Bruce Kellett wrote:
> >
> > Of course A(x) and B(x) refer to the same point on the screen. That is
> > not a collapse, that is just what the notation means.
>
> A(x) and B(x) considered as the representations of |A> and |B> in the
> position basis, i.e.  A(x) =  and B(x) =  are still orthogonal
> states, as they represent the orthogonal states |A> and |B>:
>
> 0 =  = Integral over x of d^3x =  Integral over x of
> A*(x)B(x) d^3x
>
> But you interpret this as the total counts of particles on the entire
> screen not changing which you call an absence of interference. However
> interference is what we detect locally on each point on the screen. You
> can't say that for each point x0 on the screen,  A(x0) and B(x0) are
> particle states. These values are not the quantum states of the particle
> before it hits the screen, unless you would have done a measurement
> localizing the particle near x0.
>

The spot on the screen may well be such an experiment.

> So, your argument only makes sense if you invoke collapse via a position
> measurement.
>

You over-elaborate a simple schematic. My A(x) and B(x) are simply the
amplitudes of the wave function at point x on the screen from the two
slits. To get the intensity at x, you add the amplitudes and take the
modulus squared -- you do not add the intensities from each slit separately.

Perhaps the problem stems from my using the ket vector representation for
single complex numbers. But complex numbers are never orthogonal, so using
the ket generalises this interference result to general state vectors.
Integrating over the screen is not relevant to the intensity at each point.

Bruce

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Re: STEP 3

2019-08-13 Thread smitra


On 13-08-2019 13:33, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 7:41 PM smitra  wrote:


On 13-08-2019 05:14, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 12:16 PM smitra  wrote:


On 13-08-2019 02:49, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 10:43 AM smitra 

wrote:



On 13-08-2019 01:41, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 9:09 AM smitra 

wrote:



On 12-08-2019 08:29, Bruce Kellett wrote:


Look at this another way. It is just an illustration of
complementarity. Measuring which slit the photon went

through

is

a

position measurement at the slits. Measuring the

interference

pattern

at the screen is equivalent to a momentum measurement at

the

slits.

Such measurement operators do not commute -- the

measurements

are

complementary and cannot be performed simultaneously.



It doesn't matter for orthogonality of the states whether or

not

they
are measured.


Of course it does. The slits are not orthogonal states unless

they are

measured position eigenstates. If they are not measured, they

are

individually superpositions of many position eigenstates

(including

eigenstates that overlap both slits), so the slits themselves

are

no

longer orthogonal. Orthogonal states cannot interfere, that

is

why a

position measurement at the slits makes the interference

pattern

on

the screen disappear.

The fact remains, that orthogonal states cannot interfere:

( + |B>) =  +  + 2 

and the interference term  vanishes if |A> and |B> are
orthogonal. You can't get away from this basic fact about

quantum

mechanics.



 is zero in the two slit experiment, if you integrate the
interference term over the screen you get zero.

Thing is that the interference we can observe at some position

x

on

the
screen is Re[], which for general x is nonzero

despite

the
fact that  = 0.


So you agree that if the overlap vanishes you do not get

interference.

You go to some lengths to try and avoid this fact. Saying that

the

integral over the screen vanishes is beside the point.


 is the integral over all space of  and this is
zero, but
the interference we observe at some point x on the screen is
Re[], and that's in general nonzero even for

orthogonal

|A>
and |B>.


I don't know what you are trying to prove, but that is not what

my

formula meant. What I intended was that |A> represents the wave

at the

screen coming from slit A, and |B> is the wave at the screen from

slit

B. There is already and implicit dependence on the position along

the

screen A = A(x), etc. So inserting a complete set of position

states,

int dx |x>
the

point.


The states |A> and |B> have components psi_A(x) = , and
psi_B(X) =
, these components depend on x, not the states |A> and |B>. We
can
work with these components (wavefunctions) psi_A(x), and psi_B(x)
instead of |A> and |B> describing the particle just before it
interacts
with the screen, but |A> and |B> are still orthogonal, the
wavefunctions
psi_A(x), and psi_B(x) are obviously also orthogonal. You can argue
that
when restricting the two wavefunctions in some small region near x
= x0
must yield two functions that are not orthogonal, otherwise there
cannot
be interference at x = x0. However, what you are then doing is
letting
the states collapse by letting them get localized near x0. So,
you're
not talking about |A> and |B>, you are instead talking about two
states
that are proportional to |x0>


If we take a general state |A>, which depends on x, the overlap

of two

such is , and this cannot vanish if there is to be

interference.

Classically, the intensity at x from slit A is |A|^2, and

similarly

for slit B. The fact that quantum mechanically we add amplitudes,

not

intensities, means that there is the overlap term . If this

does

not vanish, [ |A> and 
whether

the slit states are orthogonal or not. In general, they are not.


As explained above, what you call |A> and |B> are in fact both
proportional to some arbitrarily chosen |x0>. You have effectively
replaced |A> by  |x0> and |B> by  |x0>, so you are
letting
the two states collapse at some point x0 on the screen first which
yield
states that depend on x0 and then you argue on the basis that the
squared norm of what you now have should have an interference term,

which then precludes the two states being orthogonal. But you made
them
co-linear by letting them collapse at the same position first.


Of course A(x) and B(x) refer to the same point on the screen. That is
not a collapse, that is just what the notation means.


A(x) and B(x) considered as the representations of |A> and |B> in the 
position basis, i.e.  A(x) =  and B(x) =  are still orthogonal 
states, as they represent the orthogonal states |A> and |B>:


0 =  = Integral over x of d^3x =  Integral over x of 
A*(x)B(x) d^3x


But you interpret this as the total counts of particles on the entire 
screen not changing which you call an absence of interference. However 
interference is what we detect locally on each point on the

Re: STEP 3

2019-08-13 Thread Jason Resch

On Tuesday, August 13, 2019, John Clark  wrote:

> On Wed, Aug 7, 2019 at 9:40 AM Bruno Marchal  wrote:
>
> On 7 Aug 2019, at 15:08, Bruce Kellett  wrote:
>
>>
>> >> What exactly is the difference between something that it is
>> impossible in principle to detect and something that does not exist?
>>
>
>
> *> It is like the difference between the human existence and the human non
>> existence, for an alien situated in a very far away galaxy. The fact that
>> this alien cannot detect us does not make the human disappearing. *
>>
>
> You're dodging the question. We can certainly detect ourselves, and it is
> not impossible in principle for a alien in a distant galaxy to detect us,
> and that is very different from your silly phantom computations that pure
> numbers are suposed to be able to perform.
>
> > *It is like the other side of the moon before we built rocket. *
>>
>
> Nobody ever said there was a philosophical problem in observing the far
> side of the moon, it was always just a matter of engineering, but no amount
> of engineering can make your ridiculous phantom calculations real. If they
> existed it would be possible in principle to count the number of angels
> that were sitting on the head of a pin, but your non-material Turing
> Machine is hopeless.
>
>
The conversation was about other branches of the wavefunction.  (Which I
think you believe in despite not being able to see, nor them being able to
make a CPU useful to you).

Jason



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Re: STEP 3

2019-08-13 Thread John Clark

On Wed, Aug 7, 2019 at 9:40 AM Bruno Marchal  wrote:

On 7 Aug 2019, at 15:08, Bruce Kellett  wrote:

>
> >> What exactly is the difference between something that it is impossible
> in principle to detect and something that does not exist?
>

*> It is like the difference between the human existence and the human non
> existence, for an alien situated in a very far away galaxy. The fact that
> this alien cannot detect us does not make the human disappearing. *
>

You're dodging the question. We can certainly detect ourselves, and it is
not impossible in principle for a alien in a distant galaxy to detect us,
and that is very different from your silly phantom computations that pure
numbers are suposed to be able to perform.

> *It is like the other side of the moon before we built rocket. *
>

Nobody ever said there was a philosophical problem in observing the far
side of the moon, it was always just a matter of engineering, but no amount
of engineering can make your ridiculous phantom calculations real. If they
existed it would be possible in principle to count the number of angels
that were sitting on the head of a pin, but your non-material Turing
Machine is hopeless.

John K Clark

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Re: STEP 3

2019-08-13 Thread Bruce Kellett

On Tue, Aug 13, 2019 at 7:41 PM smitra  wrote:

> On 13-08-2019 05:14, Bruce Kellett wrote:
> > On Tue, Aug 13, 2019 at 12:16 PM smitra  wrote:
> >
> >> On 13-08-2019 02:49, Bruce Kellett wrote:
> >>> On Tue, Aug 13, 2019 at 10:43 AM smitra  wrote:
> >>>
>  On 13-08-2019 01:41, Bruce Kellett wrote:
> > On Tue, Aug 13, 2019 at 9:09 AM smitra 
> >> wrote:
> >
> >> On 12-08-2019 08:29, Bruce Kellett wrote:
> >>>
> >>> Look at this another way. It is just an illustration of
> >>> complementarity. Measuring which slit the photon went through
>  is
> >> a
> >>> position measurement at the slits. Measuring the interference
> >> pattern
> >>> at the screen is equivalent to a momentum measurement at the
> >> slits.
> >>> Such measurement operators do not commute -- the measurements
>  are
> >>> complementary and cannot be performed simultaneously.
> >>>
> >>
> >> It doesn't matter for orthogonality of the states whether or
> >> not
> >> they
> >> are measured.
> >
> > Of course it does. The slits are not orthogonal states unless
>  they are
> > measured position eigenstates. If they are not measured, they
> >> are
> > individually superpositions of many position eigenstates
>  (including
> > eigenstates that overlap both slits), so the slits themselves
> >> are
>  no
> > longer orthogonal. Orthogonal states cannot interfere, that is
>  why a
> > position measurement at the slits makes the interference
> >> pattern
>  on
> > the screen disappear.
> >
> > The fact remains, that orthogonal states cannot interfere:
> >
> > ( + |B>) =  +  + 2 
> >
> > and the interference term  vanishes if |A> and |B> are
> > orthogonal. You can't get away from this basic fact about
> >> quantum
> > mechanics.
> >
> 
>   is zero in the two slit experiment, if you integrate the
>  interference term over the screen you get zero.
> 
>  Thing is that the interference we can observe at some position x
> >> on
>  the
>  screen is Re[], which for general x is nonzero despite
>  the
>  fact that  = 0.
> >>>
> >>> So you agree that if the overlap vanishes you do not get
> >> interference.
> >>> You go to some lengths to try and avoid this fact. Saying that
> >> the
> >>> integral over the screen vanishes is beside the point.
> >>>
> >>  is the integral over all space of  and this is
> >> zero, but
> >> the interference we observe at some point x on the screen is
> >> Re[], and that's in general nonzero even for orthogonal
> >> |A>
> >> and |B>.
> >
> > I don't know what you are trying to prove, but that is not what my
> > formula meant. What I intended was that |A> represents the wave at the
> > screen coming from slit A, and |B> is the wave at the screen from slit
> > B. There is already and implicit dependence on the position along the
> > screen A = A(x), etc. So inserting a complete set of position states,
> > int dx |x> > point.
>
> The states |A> and |B> have components psi_A(x) = , and psi_B(X) =
> , these components depend on x, not the states |A> and |B>. We can
> work with these components (wavefunctions) psi_A(x), and psi_B(x)
> instead of |A> and |B> describing the particle just before it interacts
> with the screen, but |A> and |B> are still orthogonal, the wavefunctions
> psi_A(x), and psi_B(x) are obviously also orthogonal. You can argue that
> when restricting the two wavefunctions in some small region near x = x0
> must yield two functions that are not orthogonal, otherwise there cannot
> be interference at x = x0. However, what you are then doing is letting
> the states collapse by letting them get localized near x0. So, you're
> not talking about |A> and |B>, you are instead talking about two states
> that are proportional to |x0>
>
>
> > If we take a general state |A>, which depends on x, the overlap of two
> > such is , and this cannot vanish if there is to be interference.
> > Classically, the intensity at x from slit A is |A|^2, and similarly
> > for slit B. The fact that quantum mechanically we add amplitudes, not
> > intensities, means that there is the overlap term . If this does
> > not vanish, [ |A> and  > interference. There is no more to it than that. The waves at the
> > screen are not orthogonal! It really has nothing to do with whether
> > the slit states are orthogonal or not. In general, they are not.
>
> As explained above, what you call |A> and |B> are in fact both
> proportional to some arbitrarily chosen |x0>. You have effectively
> replaced |A> by  |x0> and |B> by  |x0>, so you are letting
> the two states collapse at some point x0 on the screen first which yield
> states that depend on x0 and then you argue on the basis that the
> squared norm of what you now have should have an interference term,
> which then precludes the two states being orthogonal. But you made them
> co-linear by letting them

Re: STEP 3

2019-08-13 Thread smitra

On 13-08-2019 10:21, Philip Thrift wrote:

On Monday, August 12, 2019 at 7:43:51 PM UTC-5, smitra wrote:

Thing is that the interference we can observe at some position x on
the
screen is Re[], which for general x is nonzero despite the

fact that = 0.

Saibal

To a probability (or measure) theorist, one making the conversion from
classical summing rules to quantum summing rules, this should be
easier:

https://arxiv.org/pdf/gr-qc/9401003.pdf

Where quantum theory differs from classical mechanics (in this view)
is in its dynamics, which of course is stochastic rather than
deterministic. As such, the theory functions by furnishing
probabilities for sets of histories. More formally, it associates to a
set A of histories a non-negative real number |A|, which I will call
its quantum measure |A|; and it is this measure that enters into the
sum-rules we will be concerned with.
...

NOTIONS SUCH AS STATE-VECTORS AND OBSERVABLES NEVER APPEAR, EXCEPT FOR
THE SAKE OF COMPUTATIONAL CONVENIENCE.

...

In the two-slit experiment, for example, the probability that a
particular detector will register the arrival of the electron is
(proportional to) the measure |C| of the set C of all electron world
lines which in fact pass close enough to that detector to trigger it.
When we contemplate also blocking off one or the other slit, there are
(for a fixed detector) three sets of histories to consider: the set A
of histories which arrive at the detector after traversing the
“first” slit, the corresponding set B for the “second” slit,
and the original set C = A ∐ B, the disjoint † union of A and B.

It is of course characteristic of quantum probability that the
interference term

I(A, B) := |A ∐ B| − |A| − |B|

between the slits is not zero. The surprising thing (once one has
gotten used to the fact of interference itself) is that this violation
of the classical probability sum-rules is in a certain sense so mild,
since the corresponding sum-rule for three alternatives
remains valid.

In any case, the important thing from the standpoint of interpretation
is that the electron follows one and only one path, not somehow two at
once. If probabilities are involved, it is only because the path is
not determined in advance, just as it is
initially undetermined in a classical stochastic process.

Given the failure of the sum rule I(A, B) = 0, it is clear that
quantum probabilities cannot be interpreted in the same manner that
classical ones are wont to be interpreted, in terms of (actual or
fictitious) ensemble frequencies.

Thanks, I'll read that article.

Saibal

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Re: STEP 3

2019-08-13 Thread smitra


On 13-08-2019 05:14, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 12:16 PM smitra  wrote:


On 13-08-2019 02:49, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 10:43 AM smitra  wrote:


On 13-08-2019 01:41, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 9:09 AM smitra 

wrote:



On 12-08-2019 08:29, Bruce Kellett wrote:


Look at this another way. It is just an illustration of
complementarity. Measuring which slit the photon went through

is

a

position measurement at the slits. Measuring the interference

pattern

at the screen is equivalent to a momentum measurement at the

slits.

Such measurement operators do not commute -- the measurements

are

complementary and cannot be performed simultaneously.



It doesn't matter for orthogonality of the states whether or

not

they
are measured.


Of course it does. The slits are not orthogonal states unless

they are

measured position eigenstates. If they are not measured, they

are

individually superpositions of many position eigenstates

(including

eigenstates that overlap both slits), so the slits themselves

are

no

longer orthogonal. Orthogonal states cannot interfere, that is

why a

position measurement at the slits makes the interference

pattern

on

the screen disappear.

The fact remains, that orthogonal states cannot interfere:

( + |B>) =  +  + 2 

and the interference term  vanishes if |A> and |B> are
orthogonal. You can't get away from this basic fact about

quantum

mechanics.



 is zero in the two slit experiment, if you integrate the
interference term over the screen you get zero.

Thing is that the interference we can observe at some position x

on

the
screen is Re[], which for general x is nonzero despite
the
fact that  = 0.


So you agree that if the overlap vanishes you do not get

interference.

You go to some lengths to try and avoid this fact. Saying that

the

integral over the screen vanishes is beside the point.


 is the integral over all space of  and this is
zero, but
the interference we observe at some point x on the screen is
Re[], and that's in general nonzero even for orthogonal
|A>
and |B>.


I don't know what you are trying to prove, but that is not what my
formula meant. What I intended was that |A> represents the wave at the
screen coming from slit A, and |B> is the wave at the screen from slit
B. There is already and implicit dependence on the position along the
screen A = A(x), etc. So inserting a complete set of position states,
int dx |x>

The states |A> and |B> have components psi_A(x) = , and psi_B(X) = 
, these components depend on x, not the states |A> and |B>. We can 
work with these components (wavefunctions) psi_A(x), and psi_B(x) 
instead of |A> and |B> describing the particle just before it interacts 
with the screen, but |A> and |B> are still orthogonal, the wavefunctions 
psi_A(x), and psi_B(x) are obviously also orthogonal. You can argue that 
when restricting the two wavefunctions in some small region near x = x0 
must yield two functions that are not orthogonal, otherwise there cannot 
be interference at x = x0. However, what you are then doing is letting 
the states collapse by letting them get localized near x0. So, you're 
not talking about |A> and |B>, you are instead talking about two states 
that are proportional to |x0>




If we take a general state |A>, which depends on x, the overlap of two
such is , and this cannot vanish if there is to be interference.
Classically, the intensity at x from slit A is |A|^2, and similarly
for slit B. The fact that quantum mechanically we add amplitudes, not
intensities, means that there is the overlap term . If this does
not vanish, [ |A> and 

As explained above, what you call |A> and |B> are in fact both 
proportional to some arbitrarily chosen |x0>. You have effectively 
replaced |A> by  |x0> and |B> by  |x0>, so you are letting 
the two states collapse at some point x0 on the screen first which yield 
states that depend on x0 and then you argue on the basis that the 
squared norm of what you now have should have an interference term, 
which then precludes the two states being orthogonal. But you made them 
co-linear by letting them collapse at the same position first.


Before collapse you can write |A> in the position  representation as 
integral over |x> d^3x and similarly  B = integral over |y> 
d^3y, and we not only have that |A> and |B> are orthogonal, but also the 
simple fact that |x> and |y> are orthogonal for x not equal to y.


Saibal

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Re: STEP 3

2019-08-13 Thread Philip Thrift

On Monday, August 12, 2019 at 7:43:51 PM UTC-5, smitra wrote:
>
>
> Thing is that the interference we can observe at some position x on the 
> screen is Re[], which for general x is nonzero despite the 
> fact that  = 0. 
>
> Saibal 
>

To a probability (or measure) theorist, one making the conversion from 
classical summing rules to quantum summing rules, this should be easier:

https://arxiv.org/pdf/gr-qc/9401003.pdf

Where quantum theory differs from classical mechanics (in this view) is in 
its dynamics, which of course is stochastic rather than deterministic. As 
such, the theory functions by furnishing probabilities for sets of 
histories. More formally, it associates to a set A of histories a 
non-negative real number |A|, which I will call its quantum measure |A|; 
and it is this measure that enters into the sum-rules we will be concerned 
with.
...
*Notions such as state-vectors and observables never appear, except for the 
sake of computational convenience.*

...

In the two-slit experiment, for example, the probability that a particular 
detector will register the arrival of the electron is (proportional to) the 
measure |C| of the set C of all electron world lines which in fact pass 
close enough to that detector to trigger it. When we contemplate also 
blocking off one or the other slit, there are (for a fixed detector) three 
sets of histories to consider: the set A of histories which arrive at the 
detector after traversing the “first” slit, the corresponding set B for the 
“second” slit, and the original set C = A ∐ B, the disjoint † union of A 
and B.

It is of course characteristic of quantum probability that the interference 
term

I(A, B) := |A ∐ B| − |A| − |B|

between the slits is not zero. The surprising thing (once one has gotten 
used to the fact of interference itself) is that this violation of the 
classical probability sum-rules is in a certain sense so mild, since the 
corresponding sum-rule for three alternatives
remains valid.

In any case, the important thing from the standpoint of interpretation is 
that the electron follows one and only one path, not somehow two at once. 
If probabilities are involved, it is only because the path is not 
determined in advance, just as it is
initially undetermined in a classical stochastic process.

Given the failure of the sum rule I(A, B) = 0, it is clear that quantum 
probabilities cannot be interpreted in the same manner that classical ones 
are wont to be interpreted, in terms of (actual or fictitious) ensemble 
frequencies.

...

@philipthrift 

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Re: STEP 3

On Tue, Aug 13, 2019 at 12:16 PM smitra  wrote:

> On 13-08-2019 02:49, Bruce Kellett wrote:
> > On Tue, Aug 13, 2019 at 10:43 AM smitra  wrote:
> >
> >> On 13-08-2019 01:41, Bruce Kellett wrote:
> >>> On Tue, Aug 13, 2019 at 9:09 AM smitra  wrote:
> >>>
>  On 12-08-2019 08:29, Bruce Kellett wrote:
> >
> > Look at this another way. It is just an illustration of
> > complementarity. Measuring which slit the photon went through
> >> is
>  a
> > position measurement at the slits. Measuring the interference
>  pattern
> > at the screen is equivalent to a momentum measurement at the
>  slits.
> > Such measurement operators do not commute -- the measurements
> >> are
> > complementary and cannot be performed simultaneously.
> >
> 
>  It doesn't matter for orthogonality of the states whether or not
>  they
>  are measured.
> >>>
> >>> Of course it does. The slits are not orthogonal states unless
> >> they are
> >>> measured position eigenstates. If they are not measured, they are
> >>> individually superpositions of many position eigenstates
> >> (including
> >>> eigenstates that overlap both slits), so the slits themselves are
> >> no
> >>> longer orthogonal. Orthogonal states cannot interfere, that is
> >> why a
> >>> position measurement at the slits makes the interference pattern
> >> on
> >>> the screen disappear.
> >>>
> >>> The fact remains, that orthogonal states cannot interfere:
> >>>
> >>> ( + |B>) =  +  + 2 
> >>>
> >>> and the interference term  vanishes if |A> and |B> are
> >>> orthogonal. You can't get away from this basic fact about quantum
> >>> mechanics.
> >>>
> >>
> >>  is zero in the two slit experiment, if you integrate the
> >> interference term over the screen you get zero.
> >>
> >> Thing is that the interference we can observe at some position x on
> >> the
> >> screen is Re[], which for general x is nonzero despite
> >> the
> >> fact that  = 0.
> >
> > So you agree that if the overlap vanishes you do not get interference.
> > You go to some lengths to try and avoid this fact. Saying that the
> > integral over the screen vanishes is beside the point.
> >
>  is the integral over all space of  and this is zero, but
> the interference we observe at some point x on the screen is
> Re[], and that's in general nonzero even for orthogonal |A>
> and |B>.
>

I don't know what you are trying to prove, but that is not what my formula
meant. What I intended was that |A> represents the wave at the screen
coming from slit A, and |B> is the wave at the screen from slit B. There is
already and implicit dependence on the position along the screen A = A(x),
etc. So inserting a complete set of position states, \int dx |x>, which depends on x, the overlap of two such
is , and this cannot vanish if there is to be interference.
Classically, the intensity at x from slit A is |A|^2, and similarly for
slit B. The fact that quantum mechanically we add amplitudes, not
intensities, means that there is the overlap term . If this does not
vanish, [ |A> and https://groups.google.com/d/msgid/everything-list/CAFxXSLScH0pCEA1%2BdQm9%3DT6BwujQKz7vCVp2QQF-SNpcnSv0DQ%40mail.gmail.com.

Re: STEP 3

2019-08-12 Thread smitra

On 13-08-2019 02:49, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 10:43 AM smitra wrote:

On 13-08-2019 01:41, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 9:09 AM smitra wrote:

On 12-08-2019 08:29, Bruce Kellett wrote:

Look at this another way. It is just an illustration of
complementarity. Measuring which slit the photon went through

position measurement at the slits. Measuring the interference

pattern

at the screen is equivalent to a momentum measurement at the

slits.

Such measurement operators do not commute -- the measurements

are

complementary and cannot be performed simultaneously.

It doesn't matter for orthogonality of the states whether or not
they
are measured.

Of course it does. The slits are not orthogonal states unless

they are

measured position eigenstates. If they are not measured, they are
individually superpositions of many position eigenstates

(including

eigenstates that overlap both slits), so the slits themselves are

longer orthogonal. Orthogonal states cannot interfere, that is

why a

position measurement at the slits makes the interference pattern

the screen disappear.

The fact remains, that orthogonal states cannot interfere:

( + |B>) = + + 2

and the interference term vanishes if |A> and |B> are
orthogonal. You can't get away from this basic fact about quantum
mechanics.

is zero in the two slit experiment, if you integrate the
interference term over the screen you get zero.

Thing is that the interference we can observe at some position x on
the
screen is Re[], which for general x is nonzero despite
the
fact that = 0.

So you agree that if the overlap vanishes you do not get interference.
You go to some lengths to try and avoid this fact. Saying that the
integral over the screen vanishes is beside the point.

is the integral over all space of and this is zero, but
the interference we observe at some point x on the screen is
Re[], and that's in general nonzero even for orthogonal |A>
and |B>.

Saibal

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Re: STEP 3

On Tue, Aug 13, 2019 at 10:43 AM smitra  wrote:

> On 13-08-2019 01:41, Bruce Kellett wrote:
> > On Tue, Aug 13, 2019 at 9:09 AM smitra  wrote:
> >
> >> On 12-08-2019 08:29, Bruce Kellett wrote:
> >>>
> >>> Look at this another way. It is just an illustration of
> >>> complementarity. Measuring which slit the photon went through is
> >> a
> >>> position measurement at the slits. Measuring the interference
> >> pattern
> >>> at the screen is equivalent to a momentum measurement at the
> >> slits.
> >>> Such measurement operators do not commute -- the measurements are
> >>> complementary and cannot be performed simultaneously.
> >>>
> >>
> >> It doesn't matter for orthogonality of the states whether or not
> >> they
> >> are measured.
> >
> > Of course it does. The slits are not orthogonal states unless they are
> > measured position eigenstates. If they are not measured, they are
> > individually superpositions of many position eigenstates (including
> > eigenstates that overlap both slits), so the slits themselves are no
> > longer orthogonal. Orthogonal states cannot interfere, that is why a
> > position measurement at the slits makes the interference pattern on
> > the screen disappear.
> >
> > The fact remains, that orthogonal states cannot interfere:
> >
> > ( + |B>) =  +  + 2 
> >
> > and the interference term  vanishes if |A> and |B> are
> > orthogonal. You can't get away from this basic fact about quantum
> > mechanics.
> >
>
>  is zero in the two slit experiment, if you integrate the
> interference term over the screen you get zero.
>
> Thing is that the interference we can observe at some position x on the
> screen is Re[], which for general x is nonzero despite the
> fact that  = 0.
>

So you agree that if the overlap vanishes you do not get interference. You
go to some lengths to try and avoid this fact. Saying that the integral
over the screen vanishes is beside the point.

Bruce

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Re: STEP 3

2019-08-12 Thread smitra

On 13-08-2019 01:41, Bruce Kellett wrote:

On Tue, Aug 13, 2019 at 9:09 AM smitra wrote:

On 12-08-2019 08:29, Bruce Kellett wrote:

Look at this another way. It is just an illustration of
complementarity. Measuring which slit the photon went through is

position measurement at the slits. Measuring the interference

pattern

at the screen is equivalent to a momentum measurement at the

slits.

Such measurement operators do not commute -- the measurements are
complementary and cannot be performed simultaneously.

It doesn't matter for orthogonality of the states whether or not
they
are measured.

Of course it does. The slits are not orthogonal states unless they are
measured position eigenstates. If they are not measured, they are
individually superpositions of many position eigenstates (including
eigenstates that overlap both slits), so the slits themselves are no
longer orthogonal. Orthogonal states cannot interfere, that is why a
position measurement at the slits makes the interference pattern on
the screen disappear.

The fact remains, that orthogonal states cannot interfere:

( + |B>) = + + 2

and the interference term vanishes if |A> and |B> are
orthogonal. You can't get away from this basic fact about quantum
mechanics.

is zero in the two slit experiment, if you integrate the
interference term over the screen you get zero.

Thing is that the interference we can observe at some position x on the
screen is Re[], which for general x is nonzero despite the
fact that = 0.

Saibal

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Re: STEP 3

On Tue, Aug 13, 2019 at 9:09 AM smitra  wrote:

> On 12-08-2019 08:29, Bruce Kellett wrote:
> >
> > Look at this another way. It is just an illustration of
> > complementarity. Measuring which slit the photon went through is a
> > position measurement at the slits. Measuring the interference pattern
> > at the screen is equivalent to a momentum measurement at the slits.
> > Such measurement operators do not commute -- the measurements are
> > complementary and cannot be performed simultaneously.
> >
>
> It doesn't matter for orthogonality of the states whether or not they
> are measured.


Of course it does. The slits are not orthogonal states unless they are
measured position eigenstates. If they are not measured, they are
individually superpositions of many position eigenstates (including
eigenstates that overlap both slits), so the slits themselves are no longer
orthogonal. Orthogonal states cannot interfere, that is why a position
measurement at the slits makes the interference pattern on the screen
disappear.

The fact remains, that orthogonal states cannot interfere:

( + |B>) =  +  + 2 

and the interference term  vanishes if |A> and |B> are orthogonal. You
can't get away from this basic fact about quantum mechanics.

Bruce

It's of course true that if we measure the position at the
> screen we're measuring something else than the which way information and
> the position eigenstates are not the original  superposition. But it
> remain a fact that the state of which we're measuring the position
> operator on the screen is a superposition of two orthogonal states and
> we're then seeing an interference effect defined as the difference in
> the number of dots in the screen of the actual counts and the sum of
> what would be seen if slit 1 were cloes and slit 2 open and vice versa.
>
> Saibal
>

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Re: STEP 3

2019-08-12 Thread smitra

On 12-08-2019 08:29, Bruce Kellett wrote:

On Mon, Aug 12, 2019 at 4:09 PM Bruce Kellett
wrote:

On Mon, Aug 12, 2019 at 3:56 PM smitra wrote:

On 12-08-2019 04:06, Bruce Kellett wrote:

On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal

wrote:

In the sense you mention I am OK, but we have a slight

vocabulary

problem. Not important, if you agree that measurement are
self-entanglement, so that the superposition of the orthogonal

state

SlitA and SlitB, say some oblique (with sqrt(2) = 1) SlitA +

SlitB is

inherited by the observer “looking” which is which.

If you do not measure which slit the photon went through, then

the

superposition of slits is not broken by decoherence. But the
interference at the screen depends only on things like the

wavelength

of the light, the separation of the slits, and the distance

between

the slits and the screen. If you refine this calculation by

taking the

finite width of the slits into account, you convolute the

interference

pattern with the diffraction pattern due to finite slit width.

This is

an elementary calculation in physical optics, not even

requiring

quantum mechanics. But the waves at the screen cannot be

orthogonal,

or else they would not interfere.

The states at the screen are orthogonal because they were at the
start
and inner product is conserved under the unitary time evolution.

The sits are orthogonal if you measure which slit the photon went
through, in which case the interference pattern disappears, as
required by orthogonality. But they are not orthogonal if they are
not measured, else there would be no interference. Orthogonal states
cannot interfere.

Look at this another way. It is just an illustration of
complementarity. Measuring which slit the photon went through is a
position measurement at the slits. Measuring the interference pattern
at the screen is equivalent to a momentum measurement at the slits.
Such measurement operators do not commute -- the measurements are
complementary and cannot be performed simultaneously.

It doesn't matter for orthogonality of the states whether or not they
are measured. It's of course true that if we measure the position at the
screen we're measuring something else than the which way information and
the position eigenstates are not the original superposition. But it
remain a fact that the state of which we're measuring the position
operator on the screen is a superposition of two orthogonal states and
we're then seeing an interference effect defined as the difference in
the number of dots in the screen of the actual counts and the sum of
what would be seen if slit 1 were cloes and slit 2 open and vice versa.

Saibal

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Re: STEP 3

On Mon, Aug 12, 2019 at 7:36 PM Bruno Marchal  wrote:

> On 12 Aug 2019, at 04:06, Bruce Kellett  wrote:
>
>
> If you do not measure which slit the photon went through, then the
> superposition of slits is not broken by decoherence.
>
> Decoherence break things only if there is a collapse.
>

That is simply incorrect. I refer you again to Zurek, who works in a
basically Everettian framework, but he stresses the importance of
environmental induced superselection (einselection) in producing the
preferred pointer basis. This then breaks things, in the sense that no
other basis is stable against decoherence, and other sets of basis vectors
rapidly (in times of the order of femtoseconds) collapse on to the
preferred pointer states. This is the basis of the emergence of the
classical world from the quantum substrate. And this occurs in Everett's
relative state approach just as much as in a Copenhagen-like collapse
models.

Without collapse, even if I measure which slit the photon went through, the
> two terms of the superposition continue to exist, describing me seeing both
> outcomes, and both me feel like if there has been a collapse,
>

No, that is not really true. Complementarity plays a role. Measurement of
which slit the photon went through is incompatible with the effective
momentum measurement that gives interference at the screen. That is
essentially why the slit measurement destroys the possibility of
interference. There is an incompatibility between the measurements --
basically related to the non-commutation of position and momentum operators
and the Heisenberg uncertainty principle.

and that decoherence is physical real, but that illusion is explained by
> the formalism, in a manner similar to the WM duplication: it is just first
> person indeterminacy, not in a self-duplication, but in a self entanglement.
>

Not really true, either. Decoherence, the formation of a stable pointer
basis, and the like, are all essential for the emergence of the classical
from the quantum, and the formation of objective physical states. This is
the operation of Zurek's Quantum Darwinism -- the environment acting as
witness. So this is third person objective physics -- it is not first
person indeterminacy.

Bruce

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Re: STEP 3

On Mon, Aug 12, 2019 at 7:30 PM Bruno Marchal  wrote:

> On 11 Aug 2019, at 14:09, Bruce Kellett  wrote:
>
> It is not a matter of the difference between collapse or no-collapse
> models -- it is a matter of the basic interpretation of what Everett's
> "relative states" actually are, and why the basis problem is so important
> for Everett.
>
>
> Everett makes clear that the choice of the base os irrelevant for the
> global description,
>

Maybe for the global description, but not for recovering the results of
experience. Everett got this latter problem wrong (he probably wasn't even
aware that there was a problem.).
Zurek says:
"The basis ambiguity is not limited to pointers of measuring devices. One
can show that also very large systems (such as satellites or planets) can
evolve into very non-classical superpositions. In reality, this does not
seem to happen. So there is something that picks out certain preferred
quantum states, and makes them effectively classical. Before there is
collapse, a set of preferred states, one of which is selected by the
collapse must somehow be chosen. There is nothing in the writings of
Everett that would hint at such a criterion for such preferred states, and
nothing to hint that he was aware of this question The preferred
basis problem was settled by environment induced superselection
(einselection), usually discussed along with decoherence. When
environmental monitoring is focussed on a specific observable of the
system, its eigenstates form a pointer basis: They entangle least with the
environment (and, therefore, are least perturbed by it.) This resolves the
basic ambiguity." (Zurek, arxiv:0707.2832 July 2007)

Zurek goes on to develop this at some length, but the basic point is
stability under environmental interactions, so the permanent, objective
records of the result can be formed in the environment. This is the basis
of intersubjective agreement about the result, namely, objectivity. Quantum
Darwinism means that the results that we observe are classically stable.

and the choice of the base is done by the observer for the local
> description,
>

The observer does not chose the basis -- he might choose what to measure,
but it is the environment that ultimately decides what bases is stable, and
which other bases rapidly collapse on to states in the pointer basis.

> exactly like with digital mechanism, where the notion of universal numbers
> play the role of the base. The whole theology and physics does not depend
> on the choice of the universal machinery we posit at the start, but from
> the points if view of each relative universal numbers, such difference play
> a key role in the local happenings and predictions.
>

This is no longer quantum mechanics, nor has it anything to do with physics.

Bruce

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Re: STEP 3

2019-08-12 Thread Bruno Marchal


> On 12 Aug 2019, at 04:06, Bruce Kellett  wrote:
> 
> On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal  > wrote:
> On 9 Aug 2019, at 13:15, Bruce Kellett  > wrote:
>> On Fri, Aug 9, 2019 at 7:49 PM Bruno Marchal > > wrote:
>> On 9 Aug 2019, at 04:07, Bruce Kellett > > wrote:
>>> From: Bruno Marchal mailto:marc...@ulb.ac.be>>
> On 8 Aug 2019, at 13:59, Bruce Kellett  > wrote:
> 
> On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal  > wrote:
> If the superposition are not relevant, then I don’t have any minimal 
> physical realist account of the two slit experience, or even the 
> stability of the atoms.
> Don't be obtuse, Bruno. Of course there is a superposition of the paths 
> in the two slit experiment. But these are not orthogonal basis vectors. 
> That is why there is interference.
 
 But each path are orthogonal. See the video of Susskind, where he use 1 
 and 0 to describe the boxes where we can find by which hole the particles 
 has gone through. Then, without looking at which hole the particle has 
 gone through, we can get the interference of the wave which is obliged to 
 be taken as spread on both holes, and that represent the superposition of 
 the two orthogonal state described here as 0 and 1.
>>> I seldom watch long videos of lectures. But if Susskind is saying that the 
>>> paths taken by the particle through the two slits are orthogonal then he is 
>>> flatly wrong. Writing the paths as 1 and 0 does not make them orthogonal. 
>>> And if they were orthogonal they could not interact, and you would not get 
>>> interference. Two states |0> and |1> are orthogonal if their overlap 
>>> vanishes: <0|1> = 0. Interference comes from the overlap, so if this 
>>> vanishes, there is no interference.
>>> Either Susskind is terminally confused, or you have misrepresented him.
>>> 
>>> 
>> Or maybe you are wrong. Slit one is orthogonal to slit two, as much as spin 
>> in different direction.
>> 
>> When you observe which slit the particle went through, then yes -- the slits 
>> are then orthogonal eigenstates of the position operator.
> 
> OK. But without collapse, the observation of which slit the particle was 
> taking is only self-entanglement, and it makes the whole history “the 
> particle went through slit A + me seeing the particles going through slit A” 
> orthogonal to the whole history “the particle went through slit B + me seeing 
> the particles going through slit B”.
> 
> So, like I said, the slits are orthogonal if measured.  This is irrelevant to 
> the interference at the screen, because it is the photon waves at the screen 
> that interfere, not the slits. Orthogonal states do not interfere.
> 
> Decoherence is only self-entanglement. It spread at the speed of light, or a 
> bit below, in the environment, making hard to fuse the histories again, 
> through “amnesia”, but that explains why the superposition states are are 
> hard to maintain accessible. FAPP, we can forget the parallel histories, but, 
> only FAPP!
> 
> FAPP is the way we do physics. Metaphysics is for the birds that can't fly!
>  
>> The interference comes from the fact that we get a superposition of going 
>> through slit one + going through slit two when we send a planar 
>> monochromatic wave on the wall with the two slits, and don’t measure which 
>> slit the particle go through.
>> 
>> Yes, then the states that we are measuring are not orthogonal. You do not 
>> get interference between orthogonal states.
>>  
>> That is how Susskind explains the two slit experiment in term of 
>> entanglement. You don’t need to look at the whole video, I gave the position 
>> of this sub-talk in the video.
>> 
>> Any crisp measurement, like “which slit” gives rise to orthogonal state, 
>> which can interfere when superposed.
>> 
>> Which is essentially what I said -- orthogonal states do not interfere.
> 
> In the sense you mention I am OK, but we have a slight vocabulary problem. 
> Not important, if you agree that measurement are self-entanglement, so that 
> the superposition of the orthogonal state SlitA and SlitB, say some oblique 
> (with sqrt(2) = 1) SlitA + SlitB is inherited by the observer “looking” which 
> is which.
> 
> If you do not measure which slit the photon went through, then the 
> superposition of slits is not broken by decoherence.

Decoherence break things only if there is a collapse. Without collapse, even if 
I measure which slit the photon went through, the two terms of the 
superposition continue to exist, describing me seeing both outcomes, and both 
me feel like if there has been a collapse, and that decoherence is physical 
real, but that illusion is explained by the formalism, in a manner similar to 
the WM duplication: it is just first person indeterminacy, not in a

Re: STEP 3

2019-08-12 Thread Bruno Marchal

> On 11 Aug 2019, at 14:09, Bruce Kellett  wrote:
> 
> On Fri, Aug 9, 2019 at 7:25 PM Bruno Marchal  > wrote:
> On 9 Aug 2019, at 02:59, Bruce Kellett  > wrote:
>> On Thu, Aug 8, 2019 at 6:50 PM Bruno Marchal > > wrote:
>> > On 7 Aug 2019, at 21:04, 'Brent Meeker' via Everything List 
>> > > > > wrote:
>> > 
>> > On 8/7/2019 6:40 AM, Bruno Marchal wrote:
>> >> It is like the difference between the human existence and the human non 
>> >> existence, for an alien situated in a very far away galaxy. The fact that 
>> >> this alien cannot detect us does not make the human disappearing.
>> >> 
>> >> It is like the other side of the moon before we built rocket.
>> >> 
>> >> It is like taking our theory at fave value, instead of eliminating some 
>> >> terms in the equation by sheer coquetry.
>> > 
>> > Except in the case of quantum mechanics the theory you are saying predicts 
>> > other worlds, also predicts they are inaccessible.
>> 
>> That is right, but the theory predicts that they are indirectly playing an 
>> important role without which QM explains nothing.
>> 
>> No, the theory does not predict that these parallel worlds are playing an 
>> important role. The theory (QM) explicitly predicts that such other worlds 
>> are orthogonal to observation; they do not interact; and they are in 
>> principle inaccessible. They can, therefore, play no "important role without 
>> which QM explains nothing". I think you are very confused about how QM 
>> works, Bruce
>> 
> The theory does not predict that the superposition plays an important role.
> 
> That is not what I said. I said that parallel worlds do not play any 
> important role.

Without collapse, a parallel world is only a term in a superposition. “Parallel 
world” is the fancy name of superposition, or you can define world by using the 
interaction closure (and then they spread at the speed of light, or, like 
Deutsch, you consider them to be at the start, but that is “cheating”, as, a 
priori, we cannot know in advance which base will be used by the self-aware 
creature, so my favorite terming remains the relative state formulation. The 
word “world” is often accompanied by unwanted metaphysical assumptions.

>  
> That is simply contradicted by the two slit experiments.  No interaction does 
> not imply no statistical interference, or QM would not makes any sense at 
> all. Dirac considered the principle of superposition as the main quantum 
> feature.
> 
> “Parallel world” is the same as superposition of state/histories.
> 
>  That is where the trouble lies. Your identification of any superposition as 
> a parallel world. There is  a vast difference between superpositions and 
> parallel world, or "relative states" a la Everett.

I don’t see any, except for that  local “interaction closure” if we want 
introduce some nuance.

> 
> Any quantum state can be described as a superposition of a set of basis 
> vectors in the corresponding Hilbert space. This basis set is not unique. In 
> fact, there are an infinity of possible sets of basis vector for any Hilbert 
> space. This is just a simple observation about vector spaces.

No problem at all with this. That leads to different way to relativise the 
sates.

> 
> When you start identifying this infinity of possible basis sets with possible 
> parallel worlds, then you get into big trouble understanding quantum 
> mechanics.

Only if I add metaphysical assumption about the nature of those world. Let us 
avoid the term word, and talk only in term of relative states. Then what you 
say is just that being a superposition is relative to the choice of the base, 
and this means that I access to different states (superposed or not) according 
to what I decide to measure.

> It has long appeared to me that you have suffered from this confusion. Maybe 
> that is the real basis of the fact that we can never agree on things about 
> elementary quantum mechanics………. 

I just try to understand you. I am not sure if we differ really, except you 
seem to put a lot of metaphysics in the notion of world. You know that with 
mechanism, there is 0 world. But an appearance of many histories.

> 
> It is not a matter of the difference between collapse or no-collapse models 
> -- it is a matter of the basic interpretation of what Everett's "relative 
> states" actually are, and why the basis problem is so important for Everett.

Everett makes clear that the choice of the base os irrelevant for the global 
description, and the choice of the base is done by the observer for the local 
description, exactly like with digital mechanism, where the notion of universal 
numbers play the role of the base. The whole theology and physics does not 
depend on the choice of the universal machinery we posit at the start, but from 
the points if view of each relative universal numbers, such difference play a

Re: STEP 3

On Mon, Aug 12, 2019 at 4:09 PM Bruce Kellett  wrote:

> On Mon, Aug 12, 2019 at 3:56 PM smitra  wrote:
>
>> On 12-08-2019 04:06, Bruce Kellett wrote:
>> > On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal 
>> > wrote:
>> >
>> > In the sense you mention I am OK, but we have a slight vocabulary
>> > problem. Not important, if you agree that measurement are
>> > self-entanglement, so that the superposition of the orthogonal state
>> > SlitA and SlitB, say some oblique (with sqrt(2) = 1) SlitA + SlitB is
>> > inherited by the observer “looking” which is which.
>> >
>> > If you do not measure which slit the photon went through, then the
>> > superposition of slits is not broken by decoherence. But the
>> > interference at the screen depends only on things like the wavelength
>> > of the light, the separation of the slits, and the distance between
>> > the slits and the screen. If you refine this calculation by taking the
>> > finite width of the slits into account, you convolute the interference
>> > pattern with the diffraction pattern due to finite slit width. This is
>> > an elementary calculation in physical optics, not even requiring
>> > quantum mechanics. But the waves at the screen cannot be orthogonal,
>> > or else they would not interfere.
>>
>> The states at the screen are orthogonal because they were at the start
>> and inner product is conserved under the unitary time evolution.
>>
>
> The sits are orthogonal if you measure which slit the photon went through,
> in which case the interference pattern disappears, as required by
> orthogonality. But they are not orthogonal if they are not measured, else
> there would be no interference. Orthogonal states cannot interfere.
>

Look at this another way. It is just an illustration of complementarity.
Measuring which slit the photon went through is a position measurement at
the slits. Measuring the interference pattern at the screen is equivalent
to a momentum measurement at the slits. Such measurement operators do not
commute -- the measurements are complementary and cannot be performed
simultaneously.

Bruce

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Re: STEP 3

On Mon, Aug 12, 2019 at 3:55 PM smitra  wrote:

> On 11-08-2019 01:19, Bruce Kellett wrote:
> > On Sun, Aug 11, 2019 at 6:54 AM smitra  wrote:
> >
> > Why not? There is only one computational state for the well-defined
> > algorithm at any particular moment -- so only one "awareness".
>
> Awareness does not specify the exact algorithm, and there are vast
> number of different algorithms in the superposition.
>

Not according to the process that you have set up.

Bruce

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Re: STEP 3

On Mon, Aug 12, 2019 at 3:56 PM smitra  wrote:

> On 12-08-2019 04:06, Bruce Kellett wrote:
> > On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal 
> > wrote:
> >
> > In the sense you mention I am OK, but we have a slight vocabulary
> > problem. Not important, if you agree that measurement are
> > self-entanglement, so that the superposition of the orthogonal state
> > SlitA and SlitB, say some oblique (with sqrt(2) = 1) SlitA + SlitB is
> > inherited by the observer “looking” which is which.
> >
> > If you do not measure which slit the photon went through, then the
> > superposition of slits is not broken by decoherence. But the
> > interference at the screen depends only on things like the wavelength
> > of the light, the separation of the slits, and the distance between
> > the slits and the screen. If you refine this calculation by taking the
> > finite width of the slits into account, you convolute the interference
> > pattern with the diffraction pattern due to finite slit width. This is
> > an elementary calculation in physical optics, not even requiring
> > quantum mechanics. But the waves at the screen cannot be orthogonal,
> > or else they would not interfere.
>
> The states at the screen are orthogonal because they were at the start
> and inner product is conserved under the unitary time evolution.
>

The sits are orthogonal if you measure which slit the photon went through,
in which case the interference pattern disappears, as required by
orthogonality. But they are not orthogonal if they are not measured, else
there would be no interference. Orthogonal states cannot interfere.

Bruce

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Re: STEP 3

2019-08-11 Thread smitra


On 12-08-2019 04:06, Bruce Kellett wrote:

On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal 
wrote:


On 9 Aug 2019, at 13:15, Bruce Kellett 
wrote:

On Fri, Aug 9, 2019 at 7:49 PM Bruno Marchal 
wrote:

On 9 Aug 2019, at 04:07, Bruce Kellett 
wrote:

From: BRUNO MARCHAL 

On 8 Aug 2019, at 13:59, Bruce Kellett 
wrote:

On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal 
wrote:
If the superposition are not relevant, then I don’t have any
minimal physical realist account of the two slit experience, or even
the stability of the atoms.

Don't be obtuse, Bruno. Of course there is a superposition of the
paths in the two slit experiment. But these are not orthogonal basis
vectors. That is why there is interference.

But each path are orthogonal. See the video of Susskind, where he
use 1 and 0 to describe the boxes where we can find by which hole
the particles has gone through. Then, without looking at which hole
the particle has gone through, we can get the interference of the
wave which is obliged to be taken as spread on both holes, and that
represent the superposition of the two orthogonal state described
here as 0 and 1.


I seldom watch long videos of lectures. But if Susskind is saying that
the paths taken by the particle through the two slits are orthogonal
then he is flatly wrong. Writing the paths as 1 and 0 does not make
them orthogonal. And if they were orthogonal they could not interact,
and you would not get interference. Two states |0> and |1> are
orthogonal if their overlap vanishes: <0|1> = 0. Interference comes
from the overlap, so if this vanishes, there is no interference.

Either Susskind is terminally confused, or you have misrepresented
him.

Or maybe you are wrong. Slit one is orthogonal to slit two, as much as
spin in different direction.

When you observe which slit the particle went through, then yes -- the
slits are then orthogonal eigenstates of the position operator.

OK. But without collapse, the observation of which slit the particle
was taking is only self-entanglement, and it makes the whole history
“the particle went through slit A + me seeing the particles going
through slit A” orthogonal to the whole history “the particle went
through slit B + me seeing the particles going through slit B”.

So, like I said, the slits are orthogonal if measured.  This is
irrelevant to the interference at the screen, because it is the photon
waves at the screen that interfere, not the slits. Orthogonal states
do not interfere.


Decoherence is only self-entanglement. It spread at the speed of
light, or a bit below, in the environment, making hard to fuse the
histories again, through “amnesia”, but that explains why the
superposition states are are hard to maintain accessible. FAPP, we
can forget the parallel histories, but, only FAPP!


FAPP is the way we do physics. Metaphysics is for the birds that can't
fly!


The interference comes from the fact that we get a superposition of
going through slit one + going through slit two when we send a
planar monochromatic wave on the wall with the two slits, and
don’t measure which slit the particle go through.

Yes, then the states that we are measuring are not orthogonal. You
do not get interference between orthogonal states.

That is how Susskind explains the two slit experiment in term of
entanglement. You don’t need to look at the whole video, I gave
the position of this sub-talk in the video.

Any crisp measurement, like “which slit” gives rise to
orthogonal state, which can interfere when superposed.

Which is essentially what I said -- orthogonal states do not
interfere.


In the sense you mention I am OK, but we have a slight vocabulary
problem. Not important, if you agree that measurement are
self-entanglement, so that the superposition of the orthogonal state
SlitA and SlitB, say some oblique (with sqrt(2) = 1) SlitA + SlitB is
inherited by the observer “looking” which is which.

If you do not measure which slit the photon went through, then the
superposition of slits is not broken by decoherence. But the
interference at the screen depends only on things like the wavelength
of the light, the separation of the slits, and the distance between
the slits and the screen. If you refine this calculation by taking the
finite width of the slits into account, you convolute the interference
pattern with the diffraction pattern due to finite slit width. This is
an elementary calculation in physical optics, not even requiring
quantum mechanics. But the waves at the screen cannot be orthogonal,
or else they would not interfere.


The states at the screen are orthogonal because they were at the start 
and inner product is conserved under the unitary time evolution.


Saibal

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Re: STEP 3

2019-08-11 Thread smitra


On 11-08-2019 01:19, Bruce Kellett wrote:

On Sun, Aug 11, 2019 at 6:54 AM smitra  wrote:


On 10-08-2019 10:20, Bruce Kellett wrote:

On Sat, Aug 10, 2019 at 6:16 PM smitra  wrote:


On 10-08-2019 09:49, Bruce Kellett wrote:


But when you cannot reach, or ignore, some of this larger

number

of

degrees of freedom, you end up with a mixed state. That is how
decoherence reduces the pure state to a mixture on measurement

--

there are always degrees of freedom that are not recoverable --

those

infamous IR photons, for example. The brain does not take all

this

entanglement with the environment into account, so it is a

classical

object.



And that step of tracing out the environmental degrees of

freedom

is
where we make a mathematical approximation in order to be able

to

do
practical calculations. But as you have said in this thread, the
mathematics we use to describe a system is not necessarily a

good

physical representation of the system. It's not up to the brain

to

decide to not take entanglement into account.


No, the brain has no choice. It simply cannot take these

environmental

dof into account. So on its own reckoning, it is a classical

object.

It cannot be "classical" in the way we conventionally define it, as

that's a concept that cannot exist in the known universe.


That will be news to my table and chairs.


What we want
to do is extract an object out of an entangled state in a
physically
correct way, instead of a way that yields negligible errors when
computing expectation values of generic macroscopic observables,
but is
physically incorrect.


OK. What we want is to extract the observed classical universe from a
quantum substrate. Simply denying that this is possible is not an
option. If FAPP is the best that can be achieved, so be it. There is
no point hankering after unobtainable perfection. Progress might be
possible, but simply denying that the classical world exists is silly.


We may describe the brain
as a classical object, but that doesn't make it so.


Tell me one practical way in which this makes a difference.


There is no practical difference between a collapse interpretation
and
the MWI, neither is there a practical difference between a theory
that
says that all planets that are beyond the cosmological horizon are
made
out of green cheese and the standard astrophysical models


There is, actually. That would be to deny the cosmological hypothesis
that the universe is uniform and isotropic on the large scale. Denying
that would have local consequences.


.I do think that sticking to the relevant physics one can learn a
great
deal more than by invoking irrelevant models. E.g. in
thermodynamics we
ignore the correlations between the molecules that makes the
physical
state a specially prepared state w.r.t. inverse time evolution. So,

ignoring the correlations and pretending that everything is random
is
good enough if we focus on being able to predict measurement
outcomes,
but the fact that the state isn't just any random state follows
from the
fact that entropy would go down under time reversal while it would
increase if the state were truly random.


That depends on whether you think of time reversal as "running the
film backwards", or as reversing the sign of t in your equations.


So, the well known paradoxes in statistical physics go away when we
take
into account the way we've oversimplified the physics. In the case
of QM
exactly the same thing happens when using the density matrix
formalism
and tracing out the environment. You lose the information needed to

describe the inverse time evolution correctly. But unlike ion
statistical physics, that's not the topic under discussion. The
ignored
correlations between the degrees of freedom in the brain and the
environment do however solve a lot of other paradoxes invoked by
people
who argue that AI can never generate consciousness.

Let's consider a robot with an electronic brain that runs a well
defined
algorithm. Then there exists a notion about what algorithm the
brain is
running, and we may call this a classical description of the
electronic
brain. We include in the algorithm the exact computational state.
The
exact description of the physical state involves all the
entanglements
of all the atoms in the electronic brain and all the other local
degrees
of freedom in the environment. If we then extract the computational

state represented as a bitstring out of this state, then the exact
physical state can be written as:

|psi> = |b1>|e1> + |b2>|e2> + |b3>|e3>

where the |bj> are normalized computational states and the |ej> are
the
unnormalized "environmental" state that include everything except
the
computational state.


But you set up the problem with a well-defined algorithm, so there can
be only one computational state.


Then  is the probability for the system to
be in the state |bj>|ej>. So, it also includes the state of the
atoms in
the brain given whatever computational state the brain is in. Now

Re: STEP 3

2019-08-11 Thread Bruce Kellett

On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal  wrote:

> On 9 Aug 2019, at 13:15, Bruce Kellett  wrote:
>
> On Fri, Aug 9, 2019 at 7:49 PM Bruno Marchal  wrote:
>
>> On 9 Aug 2019, at 04:07, Bruce Kellett  wrote:
>>
>> From: Bruno Marchal 
>>
>> On 8 Aug 2019, at 13:59, Bruce Kellett  wrote:
>>
>> On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal  wrote:
>> If the superposition are not relevant, then I don’t have any minimal
>> physical realist account of the two slit experience, or even the stability
>> of the atoms.
>>
>> Don't be obtuse, Bruno. Of course there is a superposition of the paths
>> in the two slit experiment. But these are not orthogonal basis vectors.
>> That is why there is interference.
>>
>>
>> But each path are orthogonal. See the video of Susskind, where he use 1
>> and 0 to describe the boxes where we can find by which hole the particles
>> has gone through. Then, without looking at which hole the particle has gone
>> through, we can get the interference of the wave which is obliged to be
>> taken as spread on both holes, and that represent the superposition of the
>> two orthogonal state described here as 0 and 1.
>>
>> I seldom watch long videos of lectures. But if Susskind is saying that
>> the paths taken by the particle through the two slits are orthogonal then
>> he is flatly wrong. Writing the paths as 1 and 0 does not make them
>> orthogonal. And if they were orthogonal they could not interact, and you
>> would not get interference. Two states |0> and |1> are orthogonal if their
>> overlap vanishes: <0|1> = 0. Interference comes from the overlap, so if
>> this vanishes, there is no interference.
>>
>> Either Susskind is terminally confused, or you have misrepresented him.
>>
>> Or maybe you are wrong. Slit one is orthogonal to slit two, as much as
>> spin in different direction.
>>
>
> When you observe which slit the particle went through, then yes -- the
> slits are then orthogonal eigenstates of the position operator.
>
>
> OK. But without collapse, the observation of which slit the particle was
> taking is only self-entanglement, and it makes the whole history “the
> particle went through slit A + me seeing the particles going through slit
> A” orthogonal to the whole history “the particle went through slit B + me
> seeing the particles going through slit B”.
>

So, like I said, the slits are orthogonal if measured.  This is irrelevant
to the interference at the screen, because it is the photon waves at the
screen that interfere, not the slits. Orthogonal states do not interfere.

Decoherence is only self-entanglement. It spread at the speed of light, or
> a bit below, in the environment, making hard to fuse the histories again,
> through “amnesia”, but that explains why the superposition states are are
> hard to maintain accessible. FAPP, we can forget the parallel histories,
> but, only FAPP!
>

FAPP is the way we do physics. Metaphysics is for the birds that can't fly!


> The interference comes from the fact that we get a superposition of going
>> through slit one + going through slit two when we send a planar
>> monochromatic wave on the wall with the two slits, and don’t measure which
>> slit the particle go through.
>>
>
> Yes, then the states that we are measuring are not orthogonal. You do not
> get interference between orthogonal states.
>
>
>> That is how Susskind explains the two slit experiment in term of
>> entanglement. You don’t need to look at the whole video, I gave the
>> position of this sub-talk in the video.
>>
>> Any crisp measurement, like “which slit” gives rise to orthogonal state,
>> which can interfere when superposed.
>>
>
> Which is essentially what I said -- orthogonal states do not interfere.
>
>
> In the sense you mention I am OK, but we have a slight vocabulary problem.
> Not important, if you agree that measurement are self-entanglement, so that
> the superposition of the orthogonal state SlitA and SlitB, say some oblique
> (with sqrt(2) = 1) SlitA + SlitB is inherited by the observer “looking”
> which is which.
>

If you do not measure which slit the photon went through, then the
superposition of slits is not broken by decoherence. But the interference
at the screen depends only on things like the wavelength of the light, the
separation of the slits, and the distance between the slits and the screen.
If you refine this calculation by taking the finite width of the slits into
account, you convolute the interference pattern with the diffraction
pattern due to finite slit width. This is an elementary calculation in
physical optics, not even requiring quantum mechanics. But the waves at the
screen cannot be orthogonal, or else they would not interfere.

Bruce

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Re: STEP 3

2019-08-11 Thread 'Brent Meeker' via Everything List

On 8/11/2019 10:53 AM, Bruno Marchal wrote:

On 8 Aug 2019, at 21:11, 'Brent Meeker' via Everything List
wrote:

On 8/8/2019 6:27 AM, Bruno Marchal wrote:

Let us use “superposition of state” instead. The word “world” has too much
metaphysical implicit connotations.
In that case, if the computer run a superposition similar to the initial
calculation in Shor algorithm (before taking the final Fourier transform on all
superposed results), decoherence means that all computations are done on the
superposed state. That is the massive parallelism, than we can exploit through
the final Fourier Transform and measurement.

It's "massive parallelism" only in that the state vector's evolution
simultaneously has components along many different basis vectors. It's like saying a
trajectory is massively parallel because it simultaneously has components in three
dimensions.

If a point moves in a discrete 3D lattice in such a way that each components
makes different computation supporting different consciousness, that will be
counted as histories by the mechanist.

Do you suppose that consciousness can be instantiated by motion in one
axis? Can such motion implement CT computation?

And that is what happen in the “universal” wave, or any wave describing
observer coupled (but not necessarily interacting)

What is "coupled but not interacting" mean?

Brent

with a superposed quantum states, when they look up which states they are in.
Without collapse, nothing make an history more real or less real, except from
the first person view of the subjects.

Bruno

Brent

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Re: STEP 3



> On 8 Aug 2019, at 21:11, 'Brent Meeker' via Everything List 
>  wrote:
> 
> 
> 
> On 8/8/2019 6:27 AM, Bruno Marchal wrote:
>> 
>> Let us use “superposition of state” instead. The word “world” has too much 
>> metaphysical implicit connotations.
>> In that case, if the computer run a superposition similar to the initial 
>> calculation in Shor algorithm (before taking the final Fourier transform on 
>> all superposed results), decoherence means that all computations are done on 
>> the superposed state. That is the massive parallelism, than we can exploit 
>> through the final Fourier Transform and measurement.
> 
> It's "massive parallelism" only in that the state vector's evolution 
> simultaneously has components along many different basis vectors. It's like 
> saying a trajectory is massively parallel because it simultaneously has 
> components in three dimensions.

If a point moves in a discrete 3D lattice in such a way that each components 
makes different computation supporting different consciousness, that will be 
counted as histories by the mechanist.

And that is what happen in the “universal” wave, or any wave describing 
observer coupled (but not necessarily interacting) with a superposed quantum 
states, when they look up which states they are in. Without collapse, nothing 
make an history more real or less real, except from the first person view of 
the subjects.

Bruno




> 
> Brent
> 
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Re: STEP 3


> On 9 Aug 2019, at 13:15, Bruce Kellett  wrote:
> 
> On Fri, Aug 9, 2019 at 7:49 PM Bruno Marchal  > wrote:
> On 9 Aug 2019, at 04:07, Bruce Kellett  > wrote:
>> From: Bruno Marchal mailto:marc...@ulb.ac.be>>
 On 8 Aug 2019, at 13:59, Bruce Kellett >>> > wrote:
 
 On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal >>> > wrote:
 If the superposition are not relevant, then I don’t have any minimal 
 physical realist account of the two slit experience, or even the stability 
 of the atoms.
 Don't be obtuse, Bruno. Of course there is a superposition of the paths in 
 the two slit experiment. But these are not orthogonal basis vectors. That 
 is why there is interference.
>>> 
>>> But each path are orthogonal. See the video of Susskind, where he use 1 and 
>>> 0 to describe the boxes where we can find by which hole the particles has 
>>> gone through. Then, without looking at which hole the particle has gone 
>>> through, we can get the interference of the wave which is obliged to be 
>>> taken as spread on both holes, and that represent the superposition of the 
>>> two orthogonal state described here as 0 and 1.
>> I seldom watch long videos of lectures. But if Susskind is saying that the 
>> paths taken by the particle through the two slits are orthogonal then he is 
>> flatly wrong. Writing the paths as 1 and 0 does not make them orthogonal. 
>> And if they were orthogonal they could not interact, and you would not get 
>> interference. Two states |0> and |1> are orthogonal if their overlap 
>> vanishes: <0|1> = 0. Interference comes from the overlap, so if this 
>> vanishes, there is no interference.
>> Either Susskind is terminally confused, or you have misrepresented him.
>> 
>> 
> Or maybe you are wrong. Slit one is orthogonal to slit two, as much as spin 
> in different direction.
> 
> When you observe which slit the particle went through, then yes -- the slits 
> are then orthogonal eigenstates of the position operator.

OK. But without collapse, the observation of which slit the particle was taking 
is only self-entanglement, and it makes the whole history “the particle went 
through slit A + me seeing the particles going through slit A” orthogonal to 
the whole history “the particle went through slit B + me seeing the particles 
going through slit B”.

Decoherence is only self-entanglement. It spread at the speed of light, or a 
bit below, in the environment, making hard to fuse the histories again, through 
“amnesia”, but that explains why the superposition states are are hard to 
maintain accessible. FAPP, we can forget the parallel histories, but, only FAPP!




> 
> The interference comes from the fact that we get a superposition of going 
> through slit one + going through slit two when we send a planar monochromatic 
> wave on the wall with the two slits, and don’t measure which slit the 
> particle go through.
> 
> Yes, then the states that we are measuring are not orthogonal. You do not get 
> interference between orthogonal states.
>  
> That is how Susskind explains the two slit experiment in term of 
> entanglement. You don’t need to look at the whole video, I gave the position 
> of this sub-talk in the video.
> 
> Any crisp measurement, like “which slit” gives rise to orthogonal state, 
> which can interfere when superposed.
> 
> Which is essentially what I said -- orthogonal states do not interfere.

In the sense you mention I am OK, but we have a slight vocabulary problem. Not 
important, if you agree that measurement are self-entanglement, so that the 
superposition of the orthogonal state SlitA and SlitB, say some oblique (with 
sqrt(2) = 1) SlitA + SlitB is inherited by the observer “looking” which is 
which.

Bruno




> 
> Bruce 
> 
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Re: STEP 3


> On 10 Aug 2019, at 03:25, Russell Standish  wrote:
> 
> On Sat, Aug 10, 2019 at 08:53:39AM +1000, Bruce Kellett wrote:
>> On Sat, Aug 10, 2019 at 3:22 AM Jason Resch  wrote:
>> 
>>On Friday, August 9, 2019, Bruce Kellett  wrote:
>> 
>>On Fri, Aug 9, 2019 at 8:59 PM Jason Resch 
>>wrote:
>> 
>> 
>>What role do you see decoherence playing in consciousness?  In
>>other words, could you explain why shedding IR photons into an
>>external environment necessary for the mind to be conscious?
>> 
>> 
>>Consciousness is a classical phenomenon since the brain is a classical
>>object (not in a state of quantum coherence). So decoherence, and the
>>emergence of the classical from the quantum, is essential for
>>consciousness. Just as to be conscious is to be conscious of 
>> something,
>>such as the external world.
>> 
>> 
>> 
>>You appear to be extrapolating a causation from the appearance of a
>>correlation:
>>"The brain is classical, and the brain is conscious, therefore all
>>consciousness must be classical."
>> 
>>The conclusion doesn't follow from the premise.
>> 
>> 
>> Show me consciousness that does not involve decohered classical matter, such 
>> as
>> in a brain.
>>   
>> 
>>Also, is a brain really conscious of the external world, or is it 
>> conscious
>>of it's internal states?  The redness of a red apple does not exist
>>physically. Redness is an invention of the brain, which cannot be found in
>>the external world of colorless particles.
>> 
>> 
>> But the physical world does contain photons of various wavelengths -- which
>> correspond to different  colours. Correlation does not necessarily indicate
>> causation, but scientific study does reveal the underlying relations between
>> things.
>> 
>> Bruce 
>> 
> 
> Riffing further on this theme, conscious must be intimately tied up
> with a process for deriving meaning from data. Given a continuous
> ontology (eg ontic-ψ), this must involve a discretisation process -
> decoherence pretty much fits the bill here, and so Brent's often
> posed-insight that consciousness must involve an interaction between
> an observer system, and an environment that is traced over makes a lot
> of sense.
> 
> Going the other way, computationalism entails via the UDA that the
> physical world has this continuous character.

OK. (See Rau’s notion of smoothness, in Jochen Rau's "On quantum vs. classical 
probability” . cf Jason’s post https://arxiv.org/abs/0710.2119v2 



> So computationalism must
> ultimately address Brent's insight. This comes to the fore with the
> MGA - the argument breaks down when an environment is included that
> adds essential stocasticity to subsequent runs of the machine (ie only
> the original run of Klara is conscious, the recording reruns of
> Olympia are not, nor might any accidental recordings either).

I don’t use Olympia or MGA anymore. It is used only for those who assumes a 
physical primitive reality, to add absurdity to what is already not needed at 
the start. The essential stochasticity is provided by the random oracle 
inherent in the first person indeterminacy, compensated by the UD redundancy. 
The recording are not conscious, because they don’t compute, and the 
computation is in the logic-arithmetical relations (a type) and not in any 
(illusory assuming Mechanism) token or stuff.

Bruno



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> 
> 
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> Visiting Senior Research Fellowhpco...@hpcoders.com.au
> Economics, Kingston University http://www.hpcoders.com.au
> 
> 
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Re: STEP 3


> On 10 Aug 2019, at 20:34, Jason Resch  wrote:
> 
> 
> 
> On Fri, Aug 9, 2019 at 10:20 AM Bruno Marchal  > wrote:
> 
>> On 9 Aug 2019, at 13:09, Jason Resch > > wrote:
>> 
>> 
>>> 
>>> Bruno,
>>> 
>>> Forgive me if I have asked this before, but can you elaborate on the 
>>> how/why the math suggests negative interference?
>>> 
>>> I currently have no intuition for why this should be.
>>> 
>>> I recall reading something on continuous probability as being more natural 
>>> and leading to something much like the probability formulas in quantum 
>>> mechanics. Is that related?
>> 
>> 
>> It is not intuitive at all. With the UDA, we can have have the intuition 
>> coming from the first person indeterminacy on all all computational 
>> continuation in arithmetic, but in the AUDA (the Arithmetical UDA), the 
>> probabilities are constrained by the logic of self-reference G and G*. So 
>> the reason why we can hope for negative amplitude of probability comes from 
>> the fact that modal variant of the first person on the (halting) 
>> computations, which is given by the arithmetical interpretation of:
>> 
>> []p & p
>> 
>>  or
>> 
>> []p & <>t
>> 
>> or
>> 
>> []p & <>t & p
>> 
>>  With, as usual, [] = Beweisbar, and p is an arbitrary sigma_1 sentences 
>> (partial computable formula).
>> 
>> They all give a quantum logic enough close to Dalla Chiara’s presentation of 
>> them, to have the quantum features like complimentary observable, and what I 
>> have called a sort of abstract linear evolution build on a highly 
>> symmetrical core (than to LASE: the little Schroeder equation: p -> []<>p, 
>> which provides a quantisation of the sigma_1 arithmetical reality.
>> 
>> It is mainly the presence of this quantisation which justify that the 
>> probabilities behave in a quantum non boolean way, but this is hard to 
>> verify because the nesting of boxes in the G* translation makes those 
>> formula … well, probably in need of a quantum computer to be evaluated. But 
>> normally, if mechanism (and QM) are correct this should work.
>> 
>> This is explained with more detail in “Conscience et Mécanisme”.
>> 
>> Bruno
>> 
>> 
>> Thank you Bruno for your explanation and references. 
> 
> Y’re welcome.
> 
> 
>> Regarding “Conscience et Mécanisme”, is there a web/html or English version 
>> available?  Unfortunately my browser cannot do translations of PDFs but can 
>> translate web pages.  If not don't worry, I can copy and paste into a 
>> translator.
> 
> Yes, There is no HTML page for the long text. But you can consult also my 
> paper:
> 
> Marchal B. The Universal Numbers. From Biology to Physics, Progress in 
> Biophysics and Molecular Biology, 2015, Vol. 119, Issue 3, 368-381.
> https://www.ncbi.nlm.nih.gov/pubmed/26140993 
> 
> 
> You will still need some background in quantum logic, like  the paper by 
> Goldblatt which makes the link between minimal quantum logic and the B modal 
> logic. 
> 
> There is also a paper by Rawling and Selesnick which shows how to build a 
> quantum NOT gate, from the Kripke semantics of the B logic. It is not 
> entirely clear if this can be used in arithmetic, because we loss the 
> necessitation rule in “our” B logic. Open problem. A positive solution on 
> this would be a great step toward an explanation that the universal machine 
> has necessarily a quantum structure and can exploit the “parallel 
> computations in arithmetic” in the limit of the 1p indeterminacy..
> 
> Rawling JP and Selesnick SA, 2000, Orthologic and Quantum Logic: Models and 
> Computational Elements, Journal of the ACM, Vol. 47, n° 4, pp. 721-T51.
> 
> Ask question, online or here. It *is* rather technical at some point.
> 
> Bruno
> 
> 
> 
> I've been reading those references, and have found a few more which might be 
> related and of interest.  Effectively, they provide arguments for the quantum 
> probability theory based on the requirement for continuous reversible 
> operations, or the juxtaposition between finite information-carry capacity 
> and smoothness.
> 
> 
> Lucien Hardy's "Quantum Theory From Five Reasonable Axioms" 
> https://arxiv.org/abs/quant-ph/0101012 
> 
> 
> The usual formulation of quantum theory is based on rather obscure axioms 
> (employing complex Hilbert spaces, Hermitean operators, and the trace rule 
> for calculating probabilities). In this paper it is shown that quantum theory 
> can be derived from five very reasonable axioms. The first four of these are 
> obviously consistent with both quantum theory and classical probability 
> theory. Axiom 5 (which requires that there exists continuous reversible 
> transformations between pure states) rules out classical probability theory. 
> If Axiom 5 (or even just the word "continuous" from Axiom 5) is dropped then 
> we obtain classical probability theory instead. This work provides some

Re: STEP 3

2019-08-11 Thread Bruce Kellett

On Fri, Aug 9, 2019 at 7:25 PM Bruno Marchal  wrote:

> On 9 Aug 2019, at 02:59, Bruce Kellett  wrote:
>
> On Thu, Aug 8, 2019 at 6:50 PM Bruno Marchal  wrote:
>
>> > On 7 Aug 2019, at 21:04, 'Brent Meeker' via Everything List <
>> everything-list@googlegroups.com> wrote:
>> >
>> > On 8/7/2019 6:40 AM, Bruno Marchal wrote:
>> >> It is like the difference between the human existence and the human
>> non existence, for an alien situated in a very far away galaxy. The fact
>> that this alien cannot detect us does not make the human disappearing.
>> >>
>> >> It is like the other side of the moon before we built rocket.
>> >>
>> >> It is like taking our theory at fave value, instead of eliminating
>> some terms in the equation by sheer coquetry.
>> >
>> > Except in the case of quantum mechanics the theory you are saying
>> predicts other worlds, also predicts they are inaccessible.
>>
>> That is right, but the theory predicts that they are indirectly playing
>> an important role without which QM explains nothing.
>>
>
> No, the theory does not predict that these parallel worlds are playing an
> important role. The theory (QM) explicitly predicts that such other worlds
> are orthogonal to observation; they do not interact; and they are in
> principle inaccessible. They can, therefore, play no "important role
> without which QM explains nothing". I think you are very confused about how
> QM works, Bruce
>
> The theory does not predict that the superposition plays an important role.
>

That is not what I said. I said that parallel worlds do not play any
important role.


> That is simply contradicted by the two slit experiments.  No interaction
> does not imply no statistical interference, or QM would not makes any sense
> at all. Dirac considered the principle of superposition as the main quantum
> feature.
>
> “Parallel world” is the same as superposition of state/histories.
>

 That is where the trouble lies. Your identification of any superposition
as a parallel world. There is  a vast difference between superpositions and
parallel world, or "relative states" a la Everett.

Any quantum state can be described as a superposition of a set of basis
vectors in the corresponding Hilbert space. This basis set is not unique.
In fact, there are an infinity of possible sets of basis vector for any
Hilbert space. This is just a simple observation about vector spaces.

When you start identifying this infinity of possible basis sets with
possible parallel worlds, then you get into big trouble understanding
quantum mechanics. It has long appeared to me that you have suffered from
this confusion. Maybe that is the real basis of the fact that we can never
agree on things about elementary quantum mechanics..

It is not a matter of the difference between collapse or no-collapse models
-- it is a matter of the basic interpretation of what Everett's "relative
states" actually are, and why the basis problem is so important for Everett.

Bruce

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Re: STEP 3

On Sun, Aug 11, 2019 at 6:54 AM smitra  wrote:

> On 10-08-2019 10:20, Bruce Kellett wrote:
> > On Sat, Aug 10, 2019 at 6:16 PM smitra  wrote:
> >
> >> On 10-08-2019 09:49, Bruce Kellett wrote:
> >>>
> >>> But when you cannot reach, or ignore, some of this larger number
> >> of
> >>> degrees of freedom, you end up with a mixed state. That is how
> >>> decoherence reduces the pure state to a mixture on measurement --
> >>> there are always degrees of freedom that are not recoverable --
> >> those
> >>> infamous IR photons, for example. The brain does not take all
> >> this
> >>> entanglement with the environment into account, so it is a
> >> classical
> >>> object.
> >>>
> >>
> >> And that step of tracing out the environmental degrees of freedom
> >> is
> >> where we make a mathematical approximation in order to be able to
> >> do
> >> practical calculations. But as you have said in this thread, the
> >> mathematics we use to describe a system is not necessarily a good
> >> physical representation of the system. It's not up to the brain to
> >> decide to not take entanglement into account.
> >
> > No, the brain has no choice. It simply cannot take these environmental
> > dof into account. So on its own reckoning, it is a classical object.
>
> It cannot be "classical" in the way we conventionally define it, as
> that's a concept that cannot exist in the known universe.


That will be news to my table and chairs.


> What we want
> to do is extract an object out of an entangled state in a physically
> correct way, instead of a way that yields negligible errors when
> computing expectation values of generic macroscopic observables, but is
> physically incorrect.
>

OK. What we want is to extract the observed classical universe from a
quantum substrate. Simply denying that this is possible is not an option.
If FAPP is the best that can be achieved, so be it. There is no point
hankering after unobtainable perfection. Progress might be possible, but
simply denying that the classical world exists is silly.


>> We may describe the brain
> >> as a classical object, but that doesn't make it so.
> >
> > Tell me one practical way in which this makes a difference.
>
> There is no practical difference between a collapse interpretation and
> the MWI, neither is there a practical difference between a theory that
> says that all planets that are beyond the cosmological horizon are made
> out of green cheese and the standard astrophysical models


There is, actually. That would be to deny the cosmological hypothesis that
the universe is uniform and isotropic on the large scale. Denying that
would have local consequences.



> .I do think that sticking to the relevant physics one can learn a great
> deal more than by invoking irrelevant models. E.g. in thermodynamics we
> ignore the correlations between the molecules that makes the physical
> state a specially prepared state w.r.t. inverse time evolution. So,
> ignoring the correlations and pretending that everything is random is
> good enough if we focus on being able to predict measurement outcomes,
> but the fact that the state isn't just any random state follows from the
> fact that entropy would go down under time reversal while it would
> increase if the state were truly random.
>

That depends on whether you think of time reversal as "running the film
backwards", or as reversing the sign of t in your equations.


So, the well known paradoxes in statistical physics go away when we take
> into account the way we've oversimplified the physics. In the case of QM
> exactly the same thing happens when using the density matrix formalism
> and tracing out the environment. You lose the information needed to
> describe the inverse time evolution correctly. But unlike ion
> statistical physics, that's not the topic under discussion. The ignored
> correlations between the degrees of freedom in the brain and the
> environment do however solve a lot of other paradoxes invoked by people
> who argue that AI can never generate consciousness.
>
>
> Let's consider a robot with an electronic brain that runs a well defined
> algorithm. Then there exists a notion about what algorithm the brain is
> running, and we may call this a classical description of the electronic
> brain. We include in the algorithm the exact computational state. The
> exact description of the physical state involves all the entanglements
> of all the atoms in the electronic brain and all the other local degrees
> of freedom in the environment. If we then extract the computational
> state represented as a bitstring out of this state, then the exact
> physical state can be written as:
>
> |psi> = |b1>|e1> + |b2>|e2> + |b3>|e3>
>
> where the |bj> are normalized computational states and the |ej> are the
> unnormalized "environmental" state that include everything except the
> computational state.


But you set up the problem with a well-defined algorithm, so there can be
only one computational state.


> Then  is

Re: STEP 3


On 10-08-2019 10:20, Bruce Kellett wrote:

On Sat, Aug 10, 2019 at 6:16 PM smitra  wrote:


On 10-08-2019 09:49, Bruce Kellett wrote:


But when you cannot reach, or ignore, some of this larger number

of

degrees of freedom, you end up with a mixed state. That is how
decoherence reduces the pure state to a mixture on measurement --
there are always degrees of freedom that are not recoverable --

those

infamous IR photons, for example. The brain does not take all

this

entanglement with the environment into account, so it is a

classical

object.



And that step of tracing out the environmental degrees of freedom
is
where we make a mathematical approximation in order to be able to
do
practical calculations. But as you have said in this thread, the
mathematics we use to describe a system is not necessarily a good
physical representation of the system. It's not up to the brain to
decide to not take entanglement into account.


No, the brain has no choice. It simply cannot take these environmental
dof into account. So on its own reckoning, it is a classical object.


It cannot be "classical" in the way we conventionally define it, as 
that's a concept that cannot exist in the known universe. What we want 
to do is extract an object out of an entangled state in a physically 
correct way, instead of a way that yields negligible errors when 
computing expectation values of generic macroscopic observables, but is 
physically incorrect.





We may describe the brain
as a classical object, but that doesn't make it so.


Tell me one practical way in which this makes a difference.


There is no practical difference between a collapse interpretation and 
the MWI, neither is there a practical difference between a theory that 
says that all planets that are beyond the cosmological horizon are made 
out of green cheese and the standard astrophysical models.


I do think that sticking to the relevant physics one can learn a great 
deal more than by invoking irrelevant models. E.g. in thermodynamics we 
ignore the correlations between the molecules that makes the physical 
state a specially prepared state w.r.t. inverse time evolution. So, 
ignoring the correlations and pretending that everything is random is 
good enough if we focus on being able to predict measurement outcomes, 
but the fact that the state isn't just any random state follows from the 
fact that entropy would go down under time reversal while it would 
increase if the state were truly random.


So, the well known paradoxes in statistical physics go away when we take 
into account the way we've oversimplified the physics. In the case of QM 
exactly the same thing happens when using the density matrix formalism 
and tracing out the environment. You lose the information needed to 
describe the inverse time evolution correctly. But unlike ion 
statistical physics, that's not the topic under discussion. The ignored 
correlations between the degrees of freedom in the brain and the 
environment do however solve a lot of other paradoxes invoked by people 
who argue that AI can never generate consciousness.



Let's consider a robot with an electronic brain that runs a well defined 
algorithm. Then there exists a notion about what algorithm the brain is 
running, and we may call this a classical description of the electronic 
brain. We include in the algorithm the exact computational state. The 
exact description of the physical state involves all the entanglements 
of all the atoms in the electronic brain and all the other local degrees 
of freedom in the environment. If we then extract the computational 
state represented as a bitstring out of this state, then the exact 
physical state can be written as:


|psi> = |b1>|e1> + |b2>|e2> + |b3>|e3>

where the |bj> are normalized computational states and the |ej> are the 
unnormalized "environmental" state that include everything except the 
computational state. Then  is the probability for the system to 
be in the state |bj>|ej>. So, it also includes the state of the atoms in 
the brain given whatever computational state the brain is in. Now 
suppose that the robot is conscious, then what it will know/feel about 
itself and its local environment will be contained in the bistring 
describing its computational state, but the mapping from computational 
states to awareness cannot be one to one. Whatever we are aware of, 
won't precisely specify the exact computational state defined by what 
all the neurons are doing at some time. This means that there exists a 
large number of different |bj>'s that generate the exact same awareness 
for the robot.


Suppose that the robot is subjectively aware that it prepared the spin 
of an electron to be polarized in the positive in the x-direction and 
knows that I measured the spin then before I let the robot know the 
result of the measurement, the robot will find itself in the state:


|psi> = |up> + |down>]

where

|up> = sum over states where |ej> contains Saibal finding

Re: STEP 3

2019-08-10 Thread Jason Resch

On Fri, Aug 9, 2019 at 10:20 AM Bruno Marchal  wrote:

>
> On 9 Aug 2019, at 13:09, Jason Resch  wrote:
>
>
>
> On Fri, Aug 9, 2019 at 3:22 AM Bruno Marchal  wrote:
>
>>
>> On 8 Aug 2019, at 17:41, Jason Resch  wrote:
>>
>>
>>
>> On Thu, Aug 8, 2019, 5:51 AM Bruno Marchal  wrote:
>>
>>>
>>> On 8 Aug 2019, at 11:56, Bruce Kellett  wrote:
>>>
>>> On Thu, Aug 8, 2019 at 7:21 PM Bruno Marchal  wrote:
>>>
 On 8 Aug 2019, at 02:23, Bruce Kellett  wrote:

 On Wed, Aug 7, 2019 at 11:30 PM Bruno Marchal 
 wrote:

> On 7 Aug 2019, at 14:41, Bruce Kellett  wrote:
>
>
> Superpositions are fine. It is just that they do not consist of
> "parallel worlds”.
>
>
> But then by QM linearity, it is easy to prepare a superposition with
> orthogonal histories, like me seing a cat dead and me seeing a cat alive,
> when I look at the Schoredinger cat. Yes, decoherence makes hard for me to
> detect the superposition I am in, but it does not make it going away
> (unless you invoke some wave packet reduction of course)
>
>
>
>> “Parallel worlds/histories” are just a popular name to describe a
>> superposition.
>>
>
> In your dreams, maybe. There is a clear and precise definition of
> separate worlds: they are orthogonal states that do not interact. The
> absence of possible interaction means that they are not superpositions.
>
>
> That is weird.
> The branches of a superposition never interact. The point is that they
> can interfere statistically, if not there is no superposition, nor
> interference, only a mixture.
>

 There some to be some fluidity is the concepts of superposition and
 basis vectors inherent in this discussion. Any vector space can be spanned
 by a set of orthogonal basis vectors. There are an infinite number of such
 bases, plus the possibility of non-orthogonal bases given by any set of
 vectors that span the space. If the basis vectors are orthogonal, these
 basis vectors do not interact. But any general vector can be expressed as a
 superposition of these orthogonal basis vectors. (Orthonormal basis for a
 normed Hilbert space.)

 So the question whether the branches of a superposition can interact
 (interfere) or not is simply a matter of whether the branches are
 orthogonal or not. If we have a superposition of orthogonal basis vectors,
 then the branches do not interact. However, if we have a superposition of
 non-orthogonal vector, then the branches can interact.

 For example, the wave packet for a free electron is a superposition of
 momentum eigenstates (and position eigenstates). These momentum eigenstates
 are orthogonal and do not interact. The overlap function  = 0 for all
 p not equal to p'. This is the definition of orthogonal states. But this
 does not mean that the wave packet of the electron is a mixture: It is a
 pure state since there is a basis of the corresponding Hilbert space for
 which the actual state is one of the basis vectors. (We can construct an
 orthonormal set of basis vectors around this vector.)  On the other hand,
 the two paths that can be taken by a particle traversing a two-slit
 interference experiment are not orthogonal, so these paths can interact. So
 when the quantum state is written as a superposition of such paths, there
 is interference.

 Orthogonality is the key difference between things that can interfere
 and those that cannot. So if separate worlds are orthogonal, there can be
 no interference between them, and the absence of such interaction defines
 the worlds as separate.

 What I use is the fact that when we have orthogonal states, like I0>
 and I1>, I can prepare a state like (like I0> + I1>), and then I am myself
 in the superposition state Ime>( I0> + I1>), Now, in that state, I have the
 choice between measuring in the base {I0>, I1>} or in the base {I0> + I1>,
 I0> - I1>). In the first case, the “parallel” history becomes indetectoble,
 but not in the second case, so we have to take the superposition into
 account to get the prediction right in all situations.

>>>
>>> I don't think this is actually correct. Take a concrete example that we
>>> all understand. If we prepare a silver atom with spin 'up' in the
>>> x-direction, then a measurement in the x direction does not produce a
>>> superposition -- the answer is 'up' with 100% certainty. But is we measure
>>> this state in the transverse, y-direction, the result is either 'up-y' or
>>> 'down-y' with equal probabilities. This is because the initial state 'up-x'
>>> is already a superposition of 'up-y' and 'down-y'. When we measure this in
>>> the x-direction, there is no parallel history. When we measure in the
>>> y-direction, we get either 'up-y' or 'down-y'. MWI says that for either
>>>

Re: STEP 3

2019-08-10 Thread Philip Thrift



On Saturday, August 10, 2019 at 2:34:36 AM UTC-5, smitra wrote:
>
> The brain is an object that exists in our universe which 
> is described by quantum mechanics. 


To some degree, we suppose.

The obvious example of a QM event connected to to a brain: Put 
neural-probing devices in Alice's and Bob's brains that detect respectively 
the twin outputs of an EPR emitter.

@philipthrift

 

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Re: STEP 3

On Sat, Aug 10, 2019 at 6:16 PM smitra  wrote:

> On 10-08-2019 09:49, Bruce Kellett wrote:
> >
> > But when you cannot reach, or ignore, some of this larger number of
> > degrees of freedom, you end up with a mixed state. That is how
> > decoherence reduces the pure state to a mixture on measurement --
> > there are always degrees of freedom that are not recoverable -- those
> > infamous IR photons, for example. The brain does not take all this
> > entanglement with the environment into account, so it is a classical
> > object.
> >
>
> And that step of tracing out the environmental degrees of freedom is
> where we make a mathematical approximation in order to be able to do
> practical calculations. But as you have said in this thread, the
> mathematics we use to describe a system is not necessarily a good
> physical representation of the system. It's not up to the brain to
> decide to not take entanglement into account.


No, the brain has no choice. It simply cannot take these environmental dof
into account. So on its own reckoning, it is a classical object.

We may describe the brain
> as a classical object, but that doesn't make it so.
>

Tell me one practical way in which this makes a difference.

Bruce

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Re: STEP 3

On 10-08-2019 09:49, Bruce Kellett wrote:

On Sat, Aug 10, 2019 at 5:34 PM smitra wrote:

On 10-08-2019 00:53, Bruce Kellett wrote:

On Sat, Aug 10, 2019 at 3:22 AM Jason Resch

wrote:

On Friday, August 9, 2019, Bruce Kellett
wrote:

On Fri, Aug 9, 2019 at 8:59 PM Jason Resch

wrote:

What role do you see decoherence playing in consciousness? In

other

words, could you explain why shedding IR photons into an

external

environment necessary for the mind to be conscious?

Consciousness is a classical phenomenon since the brain is a
classical object (not in a state of quantum coherence). So
decoherence, and the emergence of the classical from the

quantum, is

essential for consciousness. Just as to be conscious is to be
conscious of something, such as the external world.

You appear to be extrapolating a causation from the appearance of

correlation:
"The brain is classical, and the brain is conscious, therefore

all

consciousness must be classical."

The conclusion doesn't follow from the premise.

Show me consciousness that does not involve decohered classical
matter, such as in a brain.

That's trivial. The brain is an object that exists in our universe
which
is described by quantum mechanics. Classical mechanics is a
falsified
theory that yields good approximations for macroscopic observables
due
to fast decoherence. The number of physical degrees of freedom
involved
in the entangled state the brain is part of is finite due to
locality.
This means that the brain plus a finite (but extremely large)
number of
physical degrees of freedom is always in a pure state.

But when you cannot reach, or ignore, some of this larger number of
degrees of freedom, you end up with a mixed state. That is how
decoherence reduces the pure state to a mixture on measurement --
there are always degrees of freedom that are not recoverable -- those
infamous IR photons, for example. The brain does not take all this
entanglement with the environment into account, so it is a classical
object.

And that step of tracing out the environmental degrees of freedom is
where we make a mathematical approximation in order to be able to do
practical calculations. But as you have said in this thread, the
mathematics we use to describe a system is not necessarily a good
physical representation of the system. It's not up to the brain to
decide to not take entanglement into account. We may describe the brain
as a classical object, but that doesn't make it so.

Saibal

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Re: STEP 3

On Sat, Aug 10, 2019 at 5:51 PM smitra  wrote:

> On 09-08-2019 13:49, Bruce Kellett wrote:
> > From: SMITRA 
> >
> >> On 09-08-2019 07:54, Bruce Kellett wrote:
> >>>
> >>> What is nonsense? The fact that separate states for the two slits
> >> does
> >>> not aid comprehension? Or the fact that orthogonal states do not
> >>> interfere?
> >>>
> >>
> >> Your statement that orthogonal states don't interfere is plain
> >> nonsense.
> >
> > Huh?? Did you not understand my example above of the state (|A> +
> > |B>)? There is interference in the norm only if |A> and |B> are not
> > orthogonal. This is elementary text book stuff.
>
> What you call "interference of the norm" here has nothing to do with
> interference as discussed in this thread.
>

It is just the difference between classical and quantum physics. Classical
states are orthogonal. Quantum states show interference if they are not
orthogonal.


>  What we observe at a point x on the screen is the expectation
>  value of the projection operator |x> >>>
> >>> No, we don't observe an expectation value, which is a weighted
> >> average
> >>> over possible outcomes. We measure a particular outcome at each
> >> point
> >>> on the screen.
> >>>
> >>
> >> And that's precisely given by the expectation value of the
> >> projection
> >> operator |x> >>
> >>  = psi*(x) psi(x) = |psi(x)|^2
> >
> >  That is the expectation value over all possible results. We only
> > observe one spot on the screen for each photon through the slits -- we
> > do not directly observe expectation values. The states  and 
> > are not orthogonal.
>
> The expectation value of |x> probability that the particle will be detected at position x on the
> screen. And  and  are complex numbers not states, but if you
> consider them as wavefunctions in the position representation, then they
> represent the states |0> and |1> which are orthogonal states.
>
>
> I don't understand why you keep on claiming that in the two slit
> experiment the coherent superposition of the two orthogonal states won't
> show interference. If you measure the which way information and the
> measurement result is stored coherently in a physical variable that can
> take the value 0 or 1, then we may represent the superposition as:
>
> 1/sqrt(2) [|0,0> + |1,1>]
>
> where the second component of the ket denotes the state of the system
> that measures the which way information. In this case there is no
> interference. In general, if the two states of that system are not
> orthogonal, and we denote them as |u> and |v>, then the interference
> term becomes:
>
> Re[<0|x>]
>
> So, if |u> and |v> are orthogonal then we have perfect which way
> information, and the interference term vanishes. However, it doesn't
> matter whether or not |0> and |1> are orthogonal.
>

I think the point is that we observe interference of the photon waves at
the screen, not at the slits. The slits do not interfere.

Bruce

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Re: STEP 3


On 09-08-2019 13:49, Bruce Kellett wrote:

From: SMITRA 


On 09-08-2019 07:54, Bruce Kellett wrote:

On Fri, Aug 9, 2019 at 3:16 PM smitra  wrote:


On 09-08-2019 05:35, Bruce Kellett wrote:


It is really quite simple. If a state is a sum of two

components,

|psi> = (|A> + |B>), then we measure  = (


+

|B>) =  +  + 2. If  does not vanish (the
components are not orthogonal), then there is interference. For
orthogonal components  = 0, and there is no interference.
Introducing separate states for the two slits does not aid
comprehension here.


Nonsense.


What is nonsense? The fact that separate states for the two slits

does

not aid comprehension? Or the fact that orthogonal states do not
interfere?



Your statement that orthogonal states don't interfere is plain
nonsense.


Huh?? Did you not understand my example above of the state (|A> +
|B>)? There is interference in the norm only if |A> and |B> are not
orthogonal. This is elementary text book stuff.


What you call "interference of the norm" here has nothing to do with 
interference as discussed in this thread.




What we observe at a point x on the screen is the expectation
value of the projection operator |x>

No, we don't observe an expectation value, which is a weighted

average

over possible outcomes. We measure a particular outcome at each

point

on the screen.



And that's precisely given by the expectation value of the
projection
operator |x> = psi*(x) psi(x) = |psi(x)|^2


 That is the expectation value over all possible results. We only
observe one spot on the screen for each photon through the slits -- we
do not directly observe expectation values. The states  and 
are not orthogonal.


The expectation value of |x>probability that the particle will be detected at position x on the 
screen. And  and  are complex numbers not states, but if you 
consider them as wavefunctions in the position representation, then they 
represent the states |0> and |1> which are orthogonal states.



I don't understand why you keep on claiming that in the two slit 
experiment the coherent superposition of the two orthogonal states won't 
show interference. If you measure the which way information and the 
measurement result is stored coherently in a physical variable that can 
take the value 0 or 1, then we may represent the superposition as:


1/sqrt(2) [|0,0> + |1,1>]

where the second component of the ket denotes the state of the system 
that measures the which way information. In this case there is no 
interference. In general, if the two states of that system are not 
orthogonal, and we denote them as |u> and |v>, then the interference 
term becomes:


Re[<0|x>]

So, if |u> and |v> are orthogonal then we have perfect which way 
information, and the interference term vanishes. However, it doesn't 
matter whether or not |0> and |1> are orthogonal.


Saibal

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Re: STEP 3

On Sat, Aug 10, 2019 at 5:34 PM smitra  wrote:

> On 10-08-2019 00:53, Bruce Kellett wrote:
> > On Sat, Aug 10, 2019 at 3:22 AM Jason Resch 
> > wrote:
> >
> >> On Friday, August 9, 2019, Bruce Kellett 
> >> wrote:
> >>
> >> On Fri, Aug 9, 2019 at 8:59 PM Jason Resch 
> >> wrote:
> >>
> >> What role do you see decoherence playing in consciousness? In other
> >> words, could you explain why shedding IR photons into an external
> >> environment necessary for the mind to be conscious?
> >>
> >> Consciousness is a classical phenomenon since the brain is a
> >> classical object (not in a state of quantum coherence). So
> >> decoherence, and the emergence of the classical from the quantum, is
> >> essential for consciousness. Just as to be conscious is to be
> >> conscious of something, such as the external world.
> >
> > You appear to be extrapolating a causation from the appearance of a
> > correlation:
> > "The brain is classical, and the brain is conscious, therefore all
> > consciousness must be classical."
> >
> > The conclusion doesn't follow from the premise.
> >
> > Show me consciousness that does not involve decohered classical
> > matter, such as in a brain.
>
> That's trivial. The brain is an object that exists in our universe which
> is described by quantum mechanics. Classical mechanics is a falsified
> theory that yields good approximations for macroscopic observables due
> to fast decoherence. The number of physical degrees of freedom involved
> in the entangled state the brain is part of is finite due to locality.
> This means that the brain plus a finite (but extremely large) number of
> physical degrees of freedom is always in a pure state.
>

But when you cannot reach, or ignore, some of this larger number of degrees
of freedom, you end up with a mixed state. That is how decoherence reduces
the pure state to a mixture on measurement -- there are always degrees of
freedom that are not recoverable -- those infamous IR photons, for example.
The brain does not take all this entanglement with the environment into
account, so it is a classical object.

Bruce

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Re: STEP 3

On 10-08-2019 00:53, Bruce Kellett wrote:

On Sat, Aug 10, 2019 at 3:22 AM Jason Resch
wrote:

On Friday, August 9, 2019, Bruce Kellett
wrote:

On Fri, Aug 9, 2019 at 8:59 PM Jason Resch
wrote:

What role do you see decoherence playing in consciousness? In other
words, could you explain why shedding IR photons into an external
environment necessary for the mind to be conscious?

Consciousness is a classical phenomenon since the brain is a
classical object (not in a state of quantum coherence). So
decoherence, and the emergence of the classical from the quantum, is
essential for consciousness. Just as to be conscious is to be
conscious of something, such as the external world.

You appear to be extrapolating a causation from the appearance of a
correlation:
"The brain is classical, and the brain is conscious, therefore all
consciousness must be classical."

The conclusion doesn't follow from the premise.

Show me consciousness that does not involve decohered classical
matter, such as in a brain.

That's trivial. The brain is an object that exists in our universe which
is described by quantum mechanics. Classical mechanics is a falsified
theory that yields good approximations for macroscopic observables due
to fast decoherence. The number of physical degrees of freedom involved
in the entangled state the brain is part of is finite due to locality.
This means that the brain plus a finite (but extremely large) number of
physical degrees of freedom is always in a pure state.

Saibal

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Re: STEP 3

2019-08-09 Thread Philip Thrift



On Friday, August 9, 2019 at 8:25:48 PM UTC-5, Russell Standish wrote:
>
> On Sat, Aug 10, 2019 at 08:53:39AM +1000, Bruce Kellett wrote: 
> > On Sat, Aug 10, 2019 at 3:22 AM Jason Resch  > wrote: 
> > 
> > On Friday, August 9, 2019, Bruce Kellett  > wrote: 
> > 
> > On Fri, Aug 9, 2019 at 8:59 PM Jason Resch  > 
> > wrote: 
> > 
> > 
> > What role do you see decoherence playing in consciousness?  
> In 
> > other words, could you explain why shedding IR photons into 
> an 
> > external environment necessary for the mind to be conscious? 
> > 
> > 
> > Consciousness is a classical phenomenon since the brain is a 
> classical 
> > object (not in a state of quantum coherence). So decoherence, 
> and the 
> > emergence of the classical from the quantum, is essential for 
> > consciousness. Just as to be conscious is to be conscious of 
> something, 
> > such as the external world. 
> > 
> > 
> > 
> > You appear to be extrapolating a causation from the appearance of a 
> > correlation: 
> > "The brain is classical, and the brain is conscious, therefore all 
> > consciousness must be classical." 
> > 
> > The conclusion doesn't follow from the premise. 
> > 
> > 
> > Show me consciousness that does not involve decohered classical matter, 
> such as 
> > in a brain. 
> >
> > 
> > Also, is a brain really conscious of the external world, or is it 
> conscious 
> > of it's internal states?  The redness of a red apple does not exist 
> > physically. Redness is an invention of the brain, which cannot be 
> found in 
> > the external world of colorless particles. 
> > 
> > 
> > But the physical world does contain photons of various wavelengths -- 
> which 
> > correspond to different  colours. Correlation does not necessarily 
> indicate 
> > causation, but scientific study does reveal the underlying relations 
> between 
> > things. 
> > 
> > Bruce  
> > 
>
> Riffing further on this theme, conscious must be intimately tied up 
> with a process for deriving meaning from data. Given a continuous 
> ontology (eg ontic-ψ), this must involve a discretisation process - 
> decoherence pretty much fits the bill here, and so Brent's often 
> posed-insight that consciousness must involve an interaction between 
> an observer system, and an environment that is traced over makes a lot 
> of sense. 
>
> Going the other way, computationalism entails via the UDA that the 
> physical world has this continuous character. So computationalism must 
> ultimately address Brent's insigh...





That the *physical *nature of matter is discrete but the *psychical* nature 
(of brain matter) is continuous is an interesting idea.

There is also the question of time, of which this is relevant:

"The Dynamic Theory of Time [says] time is strikingly different from the 
dimensions of space. ... The dynamic aspect of music is essential to its 
aesthetic value, and is directly tied to the dynamic aspect of time." ref: 
“Sideways Music", in (link: https://markosian.net/online-papers/) 
markosian.net/online-papers/ 


@philipthrift

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Re: STEP 3

2019-08-09 Thread Russell Standish

On Sat, Aug 10, 2019 at 08:53:39AM +1000, Bruce Kellett wrote:
> On Sat, Aug 10, 2019 at 3:22 AM Jason Resch  wrote:
> 
> On Friday, August 9, 2019, Bruce Kellett  wrote:
> 
> On Fri, Aug 9, 2019 at 8:59 PM Jason Resch 
> wrote:
> 
> 
> What role do you see decoherence playing in consciousness?  In
> other words, could you explain why shedding IR photons into an
> external environment necessary for the mind to be conscious?
> 
> 
> Consciousness is a classical phenomenon since the brain is a classical
> object (not in a state of quantum coherence). So decoherence, and the
> emergence of the classical from the quantum, is essential for
> consciousness. Just as to be conscious is to be conscious of 
> something,
> such as the external world.
> 
> 
> 
> You appear to be extrapolating a causation from the appearance of a
> correlation:
> "The brain is classical, and the brain is conscious, therefore all
> consciousness must be classical."
> 
> The conclusion doesn't follow from the premise.
> 
> 
> Show me consciousness that does not involve decohered classical matter, such 
> as
> in a brain.
>   
> 
> Also, is a brain really conscious of the external world, or is it 
> conscious
> of it's internal states?  The redness of a red apple does not exist
> physically. Redness is an invention of the brain, which cannot be found in
> the external world of colorless particles.
> 
> 
> But the physical world does contain photons of various wavelengths -- which
> correspond to different  colours. Correlation does not necessarily indicate
> causation, but scientific study does reveal the underlying relations between
> things.
> 
> Bruce 
> 

Riffing further on this theme, conscious must be intimately tied up
with a process for deriving meaning from data. Given a continuous
ontology (eg ontic-ψ), this must involve a discretisation process -
decoherence pretty much fits the bill here, and so Brent's often
posed-insight that consciousness must involve an interaction between
an observer system, and an environment that is traced over makes a lot
of sense.

Going the other way, computationalism entails via the UDA that the
physical world has this continuous character. So computationalism must
ultimately address Brent's insight. This comes to the fore with the
MGA - the argument breaks down when an environment is included that
adds essential stocasticity to subsequent runs of the machine (ie only
the original run of Klara is conscious, the recording reruns of
Olympia are not, nor might any accidental recordings either).

-- 


Dr Russell StandishPhone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Senior Research Fellowhpco...@hpcoders.com.au
Economics, Kingston University http://www.hpcoders.com.au


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Re: STEP 3

On Sat, Aug 10, 2019 at 3:22 AM Jason Resch  wrote:

> On Friday, August 9, 2019, Bruce Kellett  wrote:
>
>> On Fri, Aug 9, 2019 at 8:59 PM Jason Resch  wrote:
>>
>>>
>>> What role do you see decoherence playing in consciousness?  In other
>>> words, could you explain why shedding IR photons into an external
>>> environment necessary for the mind to be conscious?
>>>
>>
>> Consciousness is a classical phenomenon since the brain is a classical
>> object (not in a state of quantum coherence). So decoherence, and the
>> emergence of the classical from the quantum, is essential for
>> consciousness. Just as to be conscious is to be conscious of something,
>> such as the external world.
>>
>>
> You appear to be extrapolating a causation from the appearance of a
> correlation:
> "The brain is classical, and the brain is conscious, therefore all
> consciousness must be classical."
>
> The conclusion doesn't follow from the premise.
>

Show me consciousness that does not involve decohered classical matter,
such as in a brain.


> Also, is a brain really conscious of the external world, or is it
> conscious of it's internal states?  The redness of a red apple does not
> exist physically. Redness is an invention of the brain, which cannot be
> found in the external world of colorless particles.
>

But the physical world does contain photons of various wavelengths -- which
correspond to different  colours. Correlation does not necessarily indicate
causation, but scientific study does reveal the underlying relations
between things.

Bruce

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Re: STEP 3

On Friday, August 9, 2019, Bruce Kellett  wrote:

> On Fri, Aug 9, 2019 at 8:59 PM Jason Resch  wrote:
>
>>
>> What role do you see decoherence playing in consciousness?  In other
>> words, could you explain why shedding IR photons into an external
>> environment necessary for the mind to be conscious?
>>
>
> Consciousness is a classical phenomenon since the brain is a classical
> object (not in a state of quantum coherence). So decoherence, and the
> emergence of the classical from the quantum, is essential for
> consciousness. Just as to be conscious is to be conscious of something,
> such as the external world.
>
>
You appear to be extrapolating a causation from the appearance of a
correlation:
"The brain is classical, and the brain is conscious, therefore all
consciousness must be classical."

The conclusion doesn't follow from the premise.

Also, is a brain really conscious of the external world, or is it conscious
of it's internal states?  The redness of a red apple does not exist
physically. Redness is an invention of the brain, which cannot be found in
the external world of colorless particles.

Jason

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Re: STEP 3

2019-08-09 Thread Bruno Marchal

> On 9 Aug 2019, at 14:03, Bruce Kellett  wrote:
> 
> On Fri, Aug 9, 2019 at 8:19 PM Bruno Marchal  > wrote:
> 
> Contra-lucid dreams are impossible. Bruce could still claim that all dreams 
> are lucid, (like day-dreams)  and this corroborates his statement that he 
> knows when he is awake, which indeed presupposes a non digital-mechanist 
> theory of mind.
> 
> Somehow, Bruce invoke a “mystical” relations between mind and matter. He is 
> coherent with his non mechanist presupposition and his believe in a primitive 
> irreducible physical reality,
> 
> I am glad that you understand that I am doing physics, and that I am 
> expounding it correctly.

Of course. If you say so.

> If this exposition disagrees with your "mechanism", then surely that shows 
> "mechanism" to be false. After all, you claim that you test your theory by 
> its agreement or not with standard physics.

Only the collapse of the we packet would be a problem for mechanism.

> 
> obeying some wave packet reduction. He is close to Stapp and Wigner where 
> eventually consciousness is responsible for the wave packet reduction.
> 
> No, I don't believe that consciousness reduces the wave packet. Decoherence 
> does a perfectly good job of that.

Once there is no collapse, decoherence is just self-entanglement. We can forget 
the other “world” because we cannot access them, FAPP, but not FMP (For 
Metaphysical Purpose).

Our problem is that you talk physics, but sometimes seem to infer metaphysical 
proposition, like the existence of a world, or the inexistence of some worlds. 
My point is that with mechanism, a large part of the metaphysics can be tested 
experimentally. We can do metaphysics/theology with the scientific attitude 
(modesty) and method.

Unlike Clark, your metaphysical position is coherent: you seem to believe in 
atome absolute external physical reality, and in the falsity of mechanism. That 
works very well together. But my working hypothesis is Descartes Mechanism 
(modernised through Turing & Co.) and the consequence is that Plato works in 
that setting, and Aristotle (materialism) does not. Then, for those willing to 
take QM at face value, without collapse, we do get a confirmation of the 
startling consequences of (digital) Mechanism.

Bruno

> 
> Bruce 
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Re: STEP 3

2019-08-09 Thread Bruno Marchal

> On 9 Aug 2019, at 13:09, Jason Resch  wrote:
> 
> 
> 
> On Fri, Aug 9, 2019 at 3:22 AM Bruno Marchal  > wrote:
> 
>> On 8 Aug 2019, at 17:41, Jason Resch > > wrote:
>> 
>> 
>> 
>> On Thu, Aug 8, 2019, 5:51 AM Bruno Marchal > > wrote:
>> 
>>> On 8 Aug 2019, at 11:56, Bruce Kellett >> > wrote:
>>> 
>>> On Thu, Aug 8, 2019 at 7:21 PM Bruno Marchal >> > wrote:
>>> On 8 Aug 2019, at 02:23, Bruce Kellett >> > wrote:
 On Wed, Aug 7, 2019 at 11:30 PM Bruno Marchal >>> > wrote:
 On 7 Aug 2019, at 14:41, Bruce Kellett >>> > wrote:
> 
> Superpositions are fine. It is just that they do not consist of "parallel 
> worlds”.

 But then by QM linearity, it is easy to prepare a superposition with 
 orthogonal histories, like me seing a cat dead and me seeing a cat alive, 
 when I look at the Schoredinger cat. Yes, decoherence makes hard for me to 
 detect the superposition I am in, but it does not make it going away 
 (unless you invoke some wave packet reduction of course)
>  
> “Parallel worlds/histories” are just a popular name to describe a 
> superposition.
> 
> In your dreams, maybe. There is a clear and precise definition of 
> separate worlds: they are orthogonal states that do not interact. The 
> absence of possible interaction means that they are not superpositions.

 That is weird.
 The branches of a superposition never interact. The point is that they can 
 interfere statistically, if not there is no superposition, nor 
 interference, only a mixture.

 There some to be some fluidity is the concepts of superposition and basis 
 vectors inherent in this discussion. Any vector space can be spanned by a 
 set of orthogonal basis vectors. There are an infinite number of such 
 bases, plus the possibility of non-orthogonal bases given by any set of 
 vectors that span the space. If the basis vectors are orthogonal, these 
 basis vectors do not interact. But any general vector can be expressed as 
 a superposition of these orthogonal basis vectors. (Orthonormal basis for 
 a normed Hilbert space.)

 So the question whether the branches of a superposition can interact 
 (interfere) or not is simply a matter of whether the branches are 
 orthogonal or not. If we have a superposition of orthogonal basis vectors, 
 then the branches do not interact. However, if we have a superposition of 
 non-orthogonal vector, then the branches can interact.

 For example, the wave packet for a free electron is a superposition of 
 momentum eigenstates (and position eigenstates). These momentum 
 eigenstates are orthogonal and do not interact. The overlap function 
  = 0 for all p not equal to p'. This is the definition of orthogonal 
 states. But this does not mean that the wave packet of the electron is a 
 mixture: It is a pure state since there is a basis of the corresponding 
 Hilbert space for which the actual state is one of the basis vectors. (We 
 can construct an orthonormal set of basis vectors around this vector.)  On 
 the other hand, the two paths that can be taken by a particle traversing a 
 two-slit interference experiment are not orthogonal, so these paths can 
 interact. So when the quantum state is written as a superposition of such 
 paths, there is interference.

 Orthogonality is the key difference between things that can interfere and 
 those that cannot. So if separate worlds are orthogonal, there can be no 
 interference between them, and the absence of such interaction defines the 
 worlds as separate.
>>> 
>>> What I use is the fact that when we have orthogonal states, like I0> and 
>>> I1>, I can prepare a state like (like I0> + I1>), and then I am myself in 
>>> the superposition state Ime>( I0> + I1>), Now, in that state, I have the 
>>> choice between measuring in the base {I0>, I1>} or in the base {I0> + I1>, 
>>> I0> - I1>). In the first case, the “parallel” history becomes indetectoble, 
>>> but not in the second case, so we have to take the superposition into 
>>> account to get the prediction right in all situations.
>>> 
>>> I don't think this is actually correct. Take a concrete example that we all 
>>> understand. If we prepare a silver atom with spin 'up' in the x-direction, 
>>> then a measurement in the x direction does not produce a superposition -- 
>>> the answer is 'up' with 100% certainty. But is we measure this state in the 
>>> transverse, y-direction, the result is either 'up-y' or 'down-y' with equal 
>>> probabilities. This is because the initial state 'up-x' is already a 
>>> superposition of 'up-y' and 'down-y'. When we measure this

Re: STEP 3

2019-08-09 Thread Bruno Marchal


> On 9 Aug 2019, at 12:31, Philip Thrift  wrote:
> 
> 
> 
> On Friday, August 9, 2019 at 5:02:11 AM UTC-5, Bruno Marchal wrote:
> 
> Nobody experience worlds. You only experience one consciousness, but that 
> does not mean that other people are conscious, even when you cannot interact 
> with them. 
> 
> Bruno 
> 
> 
> 
> 
> This is at least a possibility, Suppose an individual consciousness goes 
> (proto-wise) down to the quantum level of histories.
> 
> cf. Quantum Measure Theory
> https://groups.google.com/forum/#!topic/everything-list/CKrX7N-DRUQ
> 
> Then there could be multiple histories of subconsciousness that integrate 
> into a single consciousness.
> 
> Nothing to do with other people, though.

No problem with this. Consciousness is absolutely real, but personal identity 
is only relatively real. Eventually, it is simple to assume only one person, 
playing a trick to itself. But that is on the fringe of being not communicable 
(in G* \ G).

Bruno



> 
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>  
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Re: STEP 3

On Fri, Aug 9, 2019 at 8:19 PM Bruno Marchal  wrote:

>
> Contra-lucid dreams are impossible. Bruce could still claim that all
> dreams are lucid, (like day-dreams)  and this corroborates his statement
> that he knows when he is awake, which indeed presupposes a non
> digital-mechanist theory of mind.
>
> Somehow, Bruce invoke a “mystical” relations between mind and matter. He
> is coherent with his non mechanist presupposition and his believe in a
> primitive irreducible physical reality,
>

I am glad that you understand that I am doing physics, and that I am
expounding it correctly. If this exposition disagrees with your
"mechanism", then surely that shows "mechanism" to be false. After all, you
claim that you test your theory by its agreement or not with standard
physics.

obeying some wave packet reduction. He is close to Stapp and Wigner where
> eventually consciousness is responsible for the wave packet reduction.
>

No, I don't believe that consciousness reduces the wave packet. Decoherence
does a perfectly good job of that.

Bruce

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Re: STEP 3


From: *smitra* mailto:smi...@zonnet.nl>>

On 09-08-2019 07:54, Bruce Kellett wrote:
> On Fri, Aug 9, 2019 at 3:16 PM smitra > wrote:

>
>> On 09-08-2019 05:35, Bruce Kellett wrote:
>>
>>> It is really quite simple. If a state is a sum of two components,
>>> |psi> = (|A> + |B>), then we measure  = (
>> +
>>> |B>) =  +  + 2. If  does not vanish (the
>>> components are not orthogonal), then there is interference. For
>>> orthogonal components  = 0, and there is no interference.
>>> Introducing separate states for the two slits does not aid
>>> comprehension here.
>>
>> Nonsense.
>
> What is nonsense? The fact that separate states for the two slits does
> not aid comprehension? Or the fact that orthogonal states do not
> interfere?
>

Your statement that orthogonal states don't interfere is plain nonsense.

Huh?? Did you not understand my example above of the state (|A> + |B>)? 
There is interference in the norm only if |A> and |B> are not 
orthogonal. This is elementary text book stuff.




>> What we observe at a point x on the screen is the expectation
>> value of the projection operator |x>
> No, we don't observe an expectation value, which is a weighted average
> over possible outcomes. We measure a particular outcome at each point
> on the screen.
>

And that's precisely given by the expectation value of the projection
operator |x> = psi*(x) psi(x) = |psi(x)|^2



That is the expectation value over all possible results. We only observe 
one spot on the screen for each photon through the slits -- we do not 
directly observe expectation values. The states  and  are not 
orthogonal.


Bruce

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Re: STEP 3

On Fri, Aug 9, 2019 at 7:39 PM Bruno Marchal  wrote:

> On 9 Aug 2019, at 03:58, Bruce Kellett  wrote:
>
> From: Bruno Marchal 
>
> On 8 Aug 2019, at 13:59, Bruce Kellett  wrote:
>
> On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal  wrote:
>
>> On 8 Aug 2019, at 11:56, Bruce Kellett  wrote:
>>
>> On Thu, Aug 8, 2019 at 7:21 PM Bruno Marchal  wrote:
>>
>>>
>>> What I use is the fact that when we have orthogonal states, like I0> and
>>> I1>, I can prepare a state like (like I0> + I1>), and then I am myself in
>>> the superposition state Ime>( I0> + I1>), Now, in that state, I have the
>>> choice between measuring in the base {I0>, I1>} or in the base {I0> + I1>,
>>> I0> - I1>). In the first case, the “parallel” history becomes indetectoble,
>>> but not in the second case, so we have to take the superposition into
>>> account to get the prediction right in all situations.
>>>
>>
>> I don't think this is actually correct. Take a concrete example that we
>> all understand. If we prepare a silver atom with spin 'up' in the
>> x-direction, then a measurement in the x direction does not produce a
>> superposition -- the answer is 'up' with 100% certainty. But is we measure
>> this state in the transverse, y-direction, the result is either 'up-y' or
>> 'down-y' with equal probabilities. This is because the initial state 'up-x'
>> is already a superposition of 'up-y' and 'down-y'. When we measure this in
>> the x-direction, there is no parallel history. When we measure in the
>> y-direction, we get either 'up-y' or 'down-y'. MWI says that for either
>> result, the alternative occurs in some other world. And that alternative
>> result is just as undetectable as the 'down-x' result for the x-measurement.
>>
>>
>>
>> The pure state up-x is the same state as the superposition of up-y and
>> down-y.
>> Me in front of up-x and Me in front of up-y + down-y are only different
>> description of the same state. When measuring that state in the
>> x-direction, I don’t made that y-superposition disappears.
>>
>
> All you are saying here is that if you measure the up-x state in the x
> direction, the state does not change -- it is still a superposition of up-y
> and down-y. Of course, if the state is not changed it does not change.
> Tautologies are not very useful.
>
>
> OK, but you are saying that “ When we measure this in the x-direction,
> there is no parallel history”, like if the superposition did disappear,
> that is why I remind the tautology. They did not.
>
> The state can still be represented as a superposition in some other basis,
> true. But this fact is of no practical significance for the operation in
> question -- measurement of the x-polarization.
>
> I think there is a basic confusion in your thinking between basis states
> and "other worlds". You want to maintain the fiction that descriptions in
> terms of alternative basis states are somehow "real". But descriptions are
> not physical states, relative or otherwise.
>
>
> But they participate in the personal histories of the superposed state of
> the observers. And they do provide many relative states.
>

There are no superposed states of the observer to which we have access. All
other relative states are orthogonal and inaccessible.


Let us use “superposition of state” instead. The word “world” has too much
> metaphysical implicit connotations.
>
> You object to the use of the word "world" in order to cover this confusion
> between basis states and worlds. A parallel world is a well-defined
> concept.
>
> We can make attempt to make it precise, like the transitive closure of
> interaction. In that case, if I look at the Schroedinger cat, I just
> entangle myself with it, and I end up in the superposition state “seeing
> the cat dead + seeing the cat alive”. Then if I interact with you, you end
> up in the superposition state “listening to me saying that the cat is
> alive” + "listening to me saying that the cat is dead”, and the entire
> universe, splits or differentiate locally through those (stepped light
> limited) interaction.
>

But, as I have just said, those other states of the superposition are
orthogonal and not accessible. They are, in terms of the definition, other
worlds.

Bruce

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Re: STEP 3

On Fri, Aug 9, 2019 at 9:04 PM Jason Resch  wrote:

> On Fri, Aug 9, 2019 at 1:49 AM Bruce Kellett 
> wrote:
>
>> On Fri, Aug 9, 2019 at 2:59 PM Bruce Kellett 
>> wrote:
>>
>>> On Fri, Aug 9, 2019 at 2:15 PM Jason Resch  wrote:
>>>

 You say this is merely a way of representing what is happening (and
 implying what I suppose to be happening is not really real), but then this
 line of reasoning fails to give any account of how Shor's algorithm factors
 the 1000 bit semi-prime.

>>>
>>> We have explained how Shor's algorithm factors the 1000 bit semi-prime:
>>> by rotations in the 2^1000dimension Hilbert space -- all one world.
>>>
>>
>> I could, perhaps, expand a bit here. You are the ones who swallow Bruno's
>> idea that the whole of physics is supported by the computations of the
>> universal dovetailer in arithmetic (platonia). Why do you then find it so
>> hard to believe that the computations to factorize large semi-prime numbers
>> cannot all be maintained in a high-dimensional abstract Hilbert space? The
>> computations there are not all that complicated -- just simple rotations of
>> a vector in  a 2^n dimensional space.
>>
>>
> I don't find it hard to believe that the computations can be maintained in
> a high-dimensional Hilbert space.  But I find it hard to believe that this
> high-dimensional Hilbert space can maintain the many components of the
> qubits but not also the many components of all the particles in the world
> and wider environment after other particles interact with those qubits.
> Nothing in the theory says the may components are eliminated, so why should
> I believe that they are?  Why do you?
>

Coherence is lost when the system interacts with randomised degrees of
freedom. It can be regarded as a thermodynamic effect -- classical
statistical mechanics.

Bruce

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Re: STEP 3

On Fri, Aug 9, 2019 at 8:59 PM Jason Resch  wrote:

>
> What role do you see decoherence playing in consciousness?  In other
> words, could you explain why shedding IR photons into an external
> environment necessary for the mind to be conscious?
>

Consciousness is a classical phenomenon since the brain is a classical
object (not in a state of quantum coherence). So decoherence, and the
emergence of the classical from the quantum, is essential for
consciousness. Just as to be conscious is to be conscious of something,
such as the external world.

Bruce

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Re: STEP 3

On Fri, Aug 9, 2019 at 7:49 PM Bruno Marchal  wrote:

> On 9 Aug 2019, at 04:07, Bruce Kellett  wrote:
>
> From: Bruno Marchal 
>
> On 8 Aug 2019, at 13:59, Bruce Kellett  wrote:
>
> On Thu, Aug 8, 2019 at 8:51 PM Bruno Marchal  wrote:
> If the superposition are not relevant, then I don’t have any minimal
> physical realist account of the two slit experience, or even the stability
> of the atoms.
>
> Don't be obtuse, Bruno. Of course there is a superposition of the paths in
> the two slit experiment. But these are not orthogonal basis vectors. That
> is why there is interference.
>
>
> But each path are orthogonal. See the video of Susskind, where he use 1
> and 0 to describe the boxes where we can find by which hole the particles
> has gone through. Then, without looking at which hole the particle has gone
> through, we can get the interference of the wave which is obliged to be
> taken as spread on both holes, and that represent the superposition of the
> two orthogonal state described here as 0 and 1.
>
> I seldom watch long videos of lectures. But if Susskind is saying that the
> paths taken by the particle through the two slits are orthogonal then he is
> flatly wrong. Writing the paths as 1 and 0 does not make them orthogonal.
> And if they were orthogonal they could not interact, and you would not get
> interference. Two states |0> and |1> are orthogonal if their overlap
> vanishes: <0|1> = 0. Interference comes from the overlap, so if this
> vanishes, there is no interference.
>
> Either Susskind is terminally confused, or you have misrepresented him.
>
> Or maybe you are wrong. Slit one is orthogonal to slit two, as much as
> spin in different direction.
>

When you observe which slit the particle went through, then yes -- the
slits are then orthogonal eigenstates of the position operator.

The interference comes from the fact that we get a superposition of going
> through slit one + going through slit two when we send a planar
> monochromatic wave on the wall with the two slits, and don’t measure which
> slit the particle go through.
>

Yes, then the states that we are measuring are not orthogonal. You do not
get interference between orthogonal states.


> That is how Susskind explains the two slit experiment in term of
> entanglement. You don’t need to look at the whole video, I gave the
> position of this sub-talk in the video.
>
> Any crisp measurement, like “which slit” gives rise to orthogonal state,
> which can interfere when superposed.
>

Which is essentially what I said -- orthogonal states do not interfere.

Bruce

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Re: STEP 3

On Fri, Aug 9, 2019 at 3:22 AM Bruno Marchal  wrote:

>
> On 8 Aug 2019, at 17:41, Jason Resch  wrote:
>
>
>
> On Thu, Aug 8, 2019, 5:51 AM Bruno Marchal  wrote:
>
>>
>> On 8 Aug 2019, at 11:56, Bruce Kellett  wrote:
>>
>> On Thu, Aug 8, 2019 at 7:21 PM Bruno Marchal  wrote:
>>
>>> On 8 Aug 2019, at 02:23, Bruce Kellett  wrote:
>>>
>>> On Wed, Aug 7, 2019 at 11:30 PM Bruno Marchal  wrote:
>>>
 On 7 Aug 2019, at 14:41, Bruce Kellett  wrote:


 Superpositions are fine. It is just that they do not consist of
 "parallel worlds”.


 But then by QM linearity, it is easy to prepare a superposition with
 orthogonal histories, like me seing a cat dead and me seeing a cat alive,
 when I look at the Schoredinger cat. Yes, decoherence makes hard for me to
 detect the superposition I am in, but it does not make it going away
 (unless you invoke some wave packet reduction of course)



> “Parallel worlds/histories” are just a popular name to describe a
> superposition.
>

 In your dreams, maybe. There is a clear and precise definition of
 separate worlds: they are orthogonal states that do not interact. The
 absence of possible interaction means that they are not superpositions.


 That is weird.
 The branches of a superposition never interact. The point is that they
 can interfere statistically, if not there is no superposition, nor
 interference, only a mixture.

>>>
>>> There some to be some fluidity is the concepts of superposition and
>>> basis vectors inherent in this discussion. Any vector space can be spanned
>>> by a set of orthogonal basis vectors. There are an infinite number of such
>>> bases, plus the possibility of non-orthogonal bases given by any set of
>>> vectors that span the space. If the basis vectors are orthogonal, these
>>> basis vectors do not interact. But any general vector can be expressed as a
>>> superposition of these orthogonal basis vectors. (Orthonormal basis for a
>>> normed Hilbert space.)
>>>
>>> So the question whether the branches of a superposition can interact
>>> (interfere) or not is simply a matter of whether the branches are
>>> orthogonal or not. If we have a superposition of orthogonal basis vectors,
>>> then the branches do not interact. However, if we have a superposition of
>>> non-orthogonal vector, then the branches can interact.
>>>
>>> For example, the wave packet for a free electron is a superposition of
>>> momentum eigenstates (and position eigenstates). These momentum eigenstates
>>> are orthogonal and do not interact. The overlap function  = 0 for all
>>> p not equal to p'. This is the definition of orthogonal states. But this
>>> does not mean that the wave packet of the electron is a mixture: It is a
>>> pure state since there is a basis of the corresponding Hilbert space for
>>> which the actual state is one of the basis vectors. (We can construct an
>>> orthonormal set of basis vectors around this vector.)  On the other hand,
>>> the two paths that can be taken by a particle traversing a two-slit
>>> interference experiment are not orthogonal, so these paths can interact. So
>>> when the quantum state is written as a superposition of such paths, there
>>> is interference.
>>>
>>> Orthogonality is the key difference between things that can interfere
>>> and those that cannot. So if separate worlds are orthogonal, there can be
>>> no interference between them, and the absence of such interaction defines
>>> the worlds as separate.
>>>
>>>
>>> What I use is the fact that when we have orthogonal states, like I0> and
>>> I1>, I can prepare a state like (like I0> + I1>), and then I am myself in
>>> the superposition state Ime>( I0> + I1>), Now, in that state, I have the
>>> choice between measuring in the base {I0>, I1>} or in the base {I0> + I1>,
>>> I0> - I1>). In the first case, the “parallel” history becomes indetectoble,
>>> but not in the second case, so we have to take the superposition into
>>> account to get the prediction right in all situations.
>>>
>>
>> I don't think this is actually correct. Take a concrete example that we
>> all understand. If we prepare a silver atom with spin 'up' in the
>> x-direction, then a measurement in the x direction does not produce a
>> superposition -- the answer is 'up' with 100% certainty. But is we measure
>> this state in the transverse, y-direction, the result is either 'up-y' or
>> 'down-y' with equal probabilities. This is because the initial state 'up-x'
>> is already a superposition of 'up-y' and 'down-y'. When we measure this in
>> the x-direction, there is no parallel history. When we measure in the
>> y-direction, we get either 'up-y' or 'down-y'. MWI says that for either
>> result, the alternative occurs in some other world. And that alternative
>> result is just as undetectable as the 'down-x' result for the x-measurement.
>>
>>
>>
>> The pure state up-x is the same state as the superposition

Re: STEP 3

On Fri, Aug 9, 2019 at 1:49 AM Bruce Kellett  wrote:

> On Fri, Aug 9, 2019 at 2:59 PM Bruce Kellett 
> wrote:
>
>> On Fri, Aug 9, 2019 at 2:15 PM Jason Resch  wrote:
>>
>>>
>>> You say this is merely a way of representing what is happening (and
>>> implying what I suppose to be happening is not really real), but then this
>>> line of reasoning fails to give any account of how Shor's algorithm factors
>>> the 1000 bit semi-prime.
>>>
>>
>> We have explained how Shor's algorithm factors the 1000 bit semi-prime:
>> by rotations in the 2^1000dimension Hilbert space -- all one world.
>>
>
> I could, perhaps, expand a bit here. You are the ones who swallow Bruno's
> idea that the whole of physics is supported by the computations of the
> universal dovetailer in arithmetic (platonia). Why do you then find it so
> hard to believe that the computations to factorize large semi-prime numbers
> cannot all be maintained in a high-dimensional abstract Hilbert space? The
> computations there are not all that complicated -- just simple rotations of
> a vector in  a 2^n dimensional space.
>
>
I don't find it hard to believe that the computations can be maintained in
a high-dimensional Hilbert space.  But I find it hard to believe that this
high-dimensional Hilbert space can maintain the many components of the
qubits but not also the many components of all the particles in the world
and wider environment after other particles interact with those qubits.
Nothing in the theory says the may components are eliminated, so why should
I believe that they are?  Why do you?

Jason

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Re: STEP 3