On Wednesday, December 5, 2012 1:41:43 AM UTC-5, Brent wrote:
>
>  On 12/4/2012 9:14 PM, Craig Weinberg wrote: 
>
>
>
> On Tuesday, December 4, 2012 6:27:42 PM UTC-5, Brent wrote: 
>>
>>  On 12/4/2012 12:32 PM, Craig Weinberg wrote: 
>>
>>
>>
>> On Tuesday, December 4, 2012 2:52:25 PM UTC-5, Brent wrote: 
>>>
>>>  
>>> Kinda depends on what you mean by 'available'.� If the entangled 
>>> photon is allowed to hit a wall and be absorbed, it is only 'available' to 
>>> a kind of Maxwellian demon who can discern the thermal atomic motions and 
>>> trace them back to get which-way infomation - but the interference pattern 
>>> is destroyed anyway.� If the entangled photon is simply allowed to fly 
>>> out the window and off to infinity it is 'available' many years later to an 
>>> inhabitant of some extra-solar planet - and the interference pattern is 
>>> destroyed in our present.� 
>>>
>>
>> What if the inhabitant of the extra-solar planet catches the photon in a 
>> lens just like the quantum eraser?
>>  
>>
>> The interference would be destroyed.� Note that the way the experiment 
>> works (and necessarily so) is that the photons detected at the interference 
>> plane have to be post-selected to pair up with those either erased or not 
>> on the other leg.� So since an extra-solar observer could only catch a 
>> small fraction of the photons, the interference would erased in the 
>> corresponding small fraction of those hitting the interference plane.
>>  
>
> You could look for a temporal rather than spatial interference pattern. 
> That way there would be a chance that if any photons were received they 
> might continue to stream for long enough:
>
>  "The latest experiment is radically different because the slits exist in 
> time not space, and because the interference pattern appears when the 
> number of electrons at the detector is plotted as a function of their 
> energy rather than their position on a screen. The work was performed at 
> the Technical University of Vienna in collaboration with physicists from 
> the Max Born Institute in Berlin, the Max Planck Institute for Quantum 
> Optics in Munich and the University of Sarajevo. 
>
> Paulus and co-workers focused a train of pulses from a Ti:sapphire laser 
> into a chamber containing a gas of argon atoms. The pulses were so short 
> � just 5 femtoseconds � that each one contained just a few cycles of 
> the electric field. 
>
> The team was able to control the output of the laser so that all the 
> pulses were identical. The researchers could, for example, ensure that each 
> pulse contained two maxima of the electric field (thatis, two peaks with 
> large positive values) and one minimum (a peak with a large negative 
> value). There was a small probability that an atom would be ionized by one 
> or other of the maxima, which therefore played the role of the slits, with 
> the resulting electron being accelerated towards a detector. If the atom 
> was ionized by the minimum, the electron travelled in the opposite 
> direction towards a second detector. 
>
> The team registered the arrival times of the electrons at both detectors 
> and then plotted the number of electrons as a function of energy. The 
> researchers observed interference fringes at the first detector because it 
> was impossible to know if an electron counted by the detector was produced 
> during the first or second maximum. 
>
> There was no interference pattern at the second detector because all the 
> electrons were produced at the same time at the minimum. However,when the 
> phase of the laser was changed so that there was one maximum and two 
> minima, interference fringes were seen at the second detector but not at 
> the first. �We have complete which-way information and no which-way 
> information at the same time for the same electron,� says Paulus. "It 
> just depends on the direction from which we look at it."� -
> http://physicsworld.com/cws/article/news/2005/mar/02/new-look-for-classic-experiment
>  
>  
> I looked at the paper. It doesn't show the detector arrangement, but from 
> the description I don't see that it can obtain which-way and no-which-way 
> for the *same* electron.
>

I think that they are using two detectors on the same wave, so that each 
one of the twin peaks on one detector which produce no-which way 
interference patterns is also a single peak on the opposite detector which 
produces the which way no-interference pattern. It's staggered like a 
zipper.



>
>  
>   
>>  
>> What if the inhabitant naturally has eyes which function as quantum 
>> erasers?
>>  
>>
>> Those wouldn't be eyes.� The eraser focuses the photons on the same 
>> spot whichever slit they went through so the 'eyes' that would erase the 
>> information are 'eyes' that can't resolve the slits.
>>  
>
> Maybe more photoreceptors than eyes, but they can still discern light from 
> dark, so they could be used as eyes of a sort, especially if their brain 
> accumulated light-dark patterns over time...i.e. more like optical ears.
>  
>
> But if they don't detect the direction of the photon with sufficient 
> resolution then they won't act as erasers of the interference pattern.
>

Maybe it could detect a red shift? Would that be enough? I think that the 
term 'eraser' is fundamentally misguided. What it seems like is that we are 
looking at the arrow of time with a microscope, and seeing how events 
themselves are realized, through a conservation of semantic continuity.


>  
>   
>>  
>> What if the inhabitant has one eye which is a quantum eraser and one 
>> which isn't?
>>  
>>
>> Depends on which one detects the photon.
>>  
>
> Yes, that's the point. If you don't know which one, how does the 
> interference pattern know?
>  
>
> 'It knows' because you have to select out the photon detections 
> corresponding the ones whose partner went in the detector eye in order to 
> see the interference.
>

Not sure I get that.
 

>
>  
>   
>>  
>> What if the inhabitant has a cat in a box with a cyanide capsule 
>> triggered by...
>>  
>>
>> What if you read the papers yourself.
>>  
>
> I try but find the jargon distracting. 
>
>
> I don't see any jargon.� It's just that real experiments are messier and 
> have more details to explain than thought experiments.
>

That's no excuse for omitting a clear summary of what was learned and why.

Craig
 

>
> Brent
>
>  It's amazing how much clearer Leibniz and Einstein are to read - it 
> seems like they are actually trying to explain something that they 
> understand rather than impress a peer review or grant committee.
>
> Craig
> �
>  
>>  
>> Brent
>>
>>  -- 
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