On 24 Oct 2012, at 17:50, Richard Ruquist wrote:

As a first step below is Cramer's argument. But I might add that MWI
does not seem natural to me at all. Alas I have to invoke god and or
teleology to negate it. TIQM seems to invoke teleology.

Here for your convenience are the key sentences in his dismissal of MWI:
"Many Worlds Interpretation of quantum mechanics leads us to expect 6%
interception and no interference, since a photon detected at image #1
is in one universe while the same photon detected at image #2 is in
another universe, and since the two "worlds" are distinguished by
different physical outcomes, they should not interfere."
"However, what Afshar observes is that the amount of light intercepted
by the wires is very small, consistent with 0% interception."

The Alternate View      
John G. Cramer
A FAREWELL TO COPENHAGEN?

http://www.analogsf.com/0412/altview.shtml

This column is about experimental tests of the various interpretations
of quantum mechanics. The question at issue is whether we can perform
experiments that can show whether there is an "observer-created
reality" as suggested by the Copenhagen Interpretation, or a peacock’s
tail of rapidly branching alternate universes, as suggested by the
Many-Worlds Interpretation, or forward-backward in time handshakes, as
suggested by the Transactional Interpretation? Until recently, I would
have said that this was an impossible task, but a new experiment has
changed my view, and I now believe that the Copenhagen and Many-Worlds
Interpretations (at least as they are usually presented) have been
falsified by experiment.

The physical theory of quantum mechanics describes the behavior of
matter and energy at the smallest distances. It has been verified by
more than 70 years of experiments, and it is trusted by working
physicists and regularly used in the fields of atomic, nuclear, and
particle physics. However, quantum mechanics is burdened by a
dismaying array of alternative and mutually contradictory ways of
interpreting its mathematical formalism. These include the orthodox
Copenhagen Interpretation, the currently fashionable Many Worlds
Interpretation, my own Transactional Interpretation, and a number of
others.

Many (including me) have declared, with almost the certainty of a
mathematical theorem, that it is impossible to distinguish between
quantum interpretations with experimental tests. Reason: all
interpretations describe the same mathematical formalism, and it is
the formalism that makes the experimentally testable predictions. As
it turns out, while this "theorem" is not wrong, it does contain a
significant loophole. If an interpretation is not completely
consistent with the mathematical formalism, it can be tested and
indeed falsified. As we will see, that appears to be the situation
with the Copenhagen and Many-Worlds Interpretations, among many
others, while my own Transactional Interpretation easily survives the
experimental test.

The experiment that appears to falsify these venerable and widely
trusted interpretations of quantum mechanics is the Afshar Experiment.
It is a new quantum test, just performed last year, which demonstrates
the presence of complete interference in an unambiguous "which-way"
measurement of the passage of light photons through a pair of
pinholes. But before describing the Afshar Experiment, let us take a
backward look at the Copenhagen Interpretation and Neils Bohr’s famous
Principle of Complementarity.

Quantum mechanics was first formulated independently by Erwin
Schrödinger and Werner Heisenberg in the mid-1920s. Physicists usually
have a mental picture of the underlying mechanisms within theory they
are formulating, but Heisenberg had no such picture of behavior at the
atomic level. With amazing intuition and remarkable good luck, he
managed to invent a matrix-based mathematical structure that agreed
with and predicted the data from most atomic physics measurements. On
the other hand, Schrödinger did start from a definite picture in
constructing his quantum wave mechanics. Making an analogy with
massless electromagnetic waves, he constructed a similar wave equation
describing particles (e.g., electrons) with a rest mass. However, it
soon was demonstrated by Bohr and Heisenberg that while Schrödinger’s
mathematics was valid, his underlying mass-wave picture was
unworkable, and he was forced to abandon it. The net result was that
the new quantum mechanics was left as a theory with no underlying
picture or mechanism. Moreover, its mathematics was saying some quite
bizarre things about how matter and energy behaved at the atomic
level, and there seemed no way of explaining this behavior.

In the Autumn of 1926, while Heisenberg was a lecturer at Bohr’s
Institute in Copenhagen, the two men walked the streets of the ancient
city almost every day, arguing, gesturing, and sketching pictures and
equations on random scraps of paper, as they struggled to come to
grips with the puzzles and paradoxes that the quantum formalism
presented. How could an object behave as both a particle and a wave?
How could its wave description spread out in all directions, then
"collapse" to a location where it was detected like a bubble that had
been pricked. Did an electron smoothly make the transition from one
atomic orbit to another or did it undergo a "quantum jump", abruptly
disappearing from one orbit and appearing in the other? How could the
occurrence of seemingly random quantum events be predicted?

The Copenhagen autumn phased into winter, and no solution was found.
In February of 1927, Bohr went away on a skiing vacation, and while he
was gone, Heisenberg discovered a key piece to the puzzle concealed in
the mathematics of Schrödinger’s wave mechanics. When one tried to
"localize" the position of an electron by specifying its location more
and more precisely, the mathematics required that the momentum (mass
times velocity) of the electron must become less localized and more
uncertain. One had to add more and more wave components with different
momentum values to make the position peak sharper. Knowledge of
position and momentum were like the two ends of a seesaw: lowering one
raised the other. The product of the uncertainties in position and
momentum could not be reduced below a lower limit, which was Planck’s
constant. The mathematics required that any attempt to do so must
fail. This became the essence of the Heisenberg Uncertainty Principle,
first published in early 1927.

When Bohr returned to Copenhagen, he was presented with the new idea.
At first he was skeptical, because of problems with Heisenberg’s
"gamma ray microscope" example used in the paper, but he finally
convinced himself that, example or not, the basic idea was correct.
The Uncertainty Principle brought Bohr to a new insight into quantum
behavior. Position and momentum were "complementary," in the sense
that precise knowledge of one excluded knowledge of the other, yet
they were jointly essential for a complete description of quantum
events. Bohr extended the idea of complementary variables to energy
and time and to particle and wave behavior. One must choose either the
particle mode, with localized positions, trajectories, and energy
quanta, or the wave mode, with spreading wave functions,
delocalization and interference. The Uncertainty Principle allowed
both descriptions within the same mathematical framework because each
excluded the other. Bohr’s Complementarity and Heisenberg’s
Uncertainty, along with the statistical interpretation of
Schrödinger’s wave functions and the view of the wave function as
observer knowledge were all interconnected to form the new Copenhagen
Interpretation.

In Bohr’s words: ". . . we are presented with a choice of either
tracing the path of the particle, or observing interference effects .
. . we have to do with a typical example of how the complementary
phenomena appear under mutually exclusive experimental arrangements."
In the context of a two-slit welcher weg (which-way) experiment, the
Principle of Complementarity dictates "the observation of an
interference pattern and the acquisition of which-way information are
mutually exclusive." By 1927 the Copenhagen Interpretation was the big
news in physics and the subject of well-attended lectures by Bohr,
Born, and Heisenberg. In the next decade, through many more lectures
and demonstrations of the effectiveness of the ideas and despite the
objections of Albert Einstein, it was canonized as the Standard
Interpretation of quantum mechanics, and it has held this somewhat
shaky position ever since.

The Afshar experiment was first performed last year by Shariar S.
Afshar and repeated while he was a Visiting Scientist at Harvard. In a
very subtle way it directly tests the Copenhagen assertion that the
observation of an interference pattern and the acquisition of particle
path which-way information are mutually exclusive. The experiment
consists of two pinholes in an opaque sheet illuminated by a laser.
The light passing through the pinholes forms an interference pattern,
a zebra-stripe set of maxima and zeroes of light intensity that can be
recorded by a digital camera. The precise locations of the
interference minimum positions, the places where the light intensity
goes to zero, are carefully measured and recorded.

Behind the plane where the interference pattern forms, Afshar places a
lens that forms an image of each pinhole at a second plane. A light
flash observed at image #1 on this plane indicates unambiguously that
a photon of light has passed through pinhole #1, and a flash at image
#2 similarly indicates that the photon has passed through pinhole #2.
Observation of the photon flashes therefore provides particle path
which-way information, as described by Bohr. According to the
Copenhagen Interpretation, in this situation all wave-mode
interference effects must be excluded.

However, at this point, Afshar introduces a new element to the
experiment. He places one or more wires at the previously measured
positions of the interference minima. In one such setup, if the wire
plane is uniformly illuminated, the wires absorb about 6% of the
light. Then Afshar measures the difference in the light received at
the pinhole images with and without the wires in place.

We are led by the Copenhagen Interpretation to expect that the
positions of the interference minima should have no particular
significance, and that the wires should intercept 6% of the light they
do for uniform illumination. Similarly, the usual form of the Many
Worlds Interpretation of quantum mechanics leads us to expect 6%
interception and no interference, since a photon detected at image #1
is in one universe while the same photon detected at image #2 is in
another universe, and since the two "worlds" are distinguished by
different physical outcomes, they should not interfere.

However, what Afshar observes is that the amount of light intercepted
by the wires is very small, consistent with 0% interception. There are
still locations of zero intensity and the wave interference pattern is
still present in the which-way measurement. Wires which are placed at
the zero-intensity locations of the interference minima intercept no
light. Thus, it appears that both the Copenhagen Interpretation and
the Many-Worlds Interpretation have been falsified by experiment.

Does this mean that the theory of quantum mechanics has also been
falsified? No indeed! The quantum formalism has no problem in
predicting the Afshar result. A simple quantum mechanical calculation
using the standard formalism shows that the wires should intercept
only a very small fraction of the light. The problem encountered by
the Copenhagen and Many-Worlds Interpretations is that the Afshar
Experiment has identified a situation in which these popular
interpretations of quantum mechanics are inconsistent with the quantum
formalism itself.

What about the Transactional Interpretation, which describes each
quantum process as a handshake between a normal "offer" wave (y) and a
back-in-time advanced "confirmation" wave (y*)? The offer waves from
the laser pass through both pinholes and cancel at the positions of
the zeroes in the interference pattern. Therefore, no transactions can
form at these locations, and the wires can intercept only a very small
amount of light. Thus, the Transactional interpretation is completely
consistent with the results of the Afshar Experiment and with the
quantum formalism.

Does this mean that the Copenhagen and Many Worlds Interpretations,
having been falsified by experiment, must be abandoned? Does it mean
that the physics community must turn to an interpretation like the
Transactional Interpretation that is consistent with the Afshar
results? Perhaps. I predict that a new generation of "Quantum Lawyers"
will begin to populate the physics literature with arguments
challenging what "is" is and claming that the wounded interpretations
never said that interference should be completely absent in a quantum
which-way measurement. And most practicing physicists who learned the
Copenhagen Interpretation at the knee of an old and beloved professor
will not abandon that mode of thinking, even if it is found to be
inconsistent with the formalism and with experiment.

But nevertheless, the rules of the game have changed. There is a way
of distinguishing between interpretations of quantum mechanics. It
will take some time for the dust to settle, but I am confident that
when it does we will have interpretations of quantum mechanics that
are on a sounder footing than the ones presently embraced by most of
the physics community.

AV Columns On-line: Electronic reprints of over 120 "The Alternate
View" columns by John G. Cramer, previously published in Analog, are
available on-line at: http://www.npl.washington.edu/av. Electronic
preprints of papers listed below are available at: http://arxiv.org.

Reference:

The Copenhagen Interpretation:
Neils Bohr, Nature 121, 580 (1928).
Neils Bohr, in: Albert Einstein: Philosopher-Scientist, P. A. Schlipp,
Ed. (Library of Living Philosophers, Evanston, Illinois, 1949).

The Transactional Interpretation:
John G. Cramer, Reviews of Modern Physics 58, 647 (1986);
http://www.npl. washington.edu/TI

The Afshar Experiment
Shariar S. Afshar, (submitted to Physical Review Letters, July, 2004);
See also http://users.rowan.edu/~afshar




Hmm; need more time to think about this. But with comp, or even without actually, the arithmetical truth, which is basically the thing I find the most independent of me, contains already the many-dreams, with a notion of many-worlds lurking on the border of the many dreams.

IF QM misses the MW, it will just mean that the physicists will have to look deeper, from a comp perspective. Our first person sharable realities are hidden at a lower level, then.

I have myself thought *many* times of devices contradicting QM, and even send them to physicists, like D'Espagnat, who helped me to find the loophole. It can be very tricky.

I think also that you can generalize Cramer's transaction view on comp, and eventually select, even in comp, a unique history, but it really look like a sort of coquetry for being alone in front of the mirror. Nature loves to multiply things, and arithmetic even more.

Bruno








On Wed, Oct 24, 2012 at 11:09 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:
Hi Richard,


On 24 Oct 2012, at 13:46, Richard Ruquist wrote:

Bruno,

What is your opinion of Cramer's Transactional Interpretation of
Quantum Mechanics TIQM,
a 4th possible interpetation of QM.

http://en.wikipedia.org/wiki/Transactional_interpretation "More
recently he [Cramer] has also argued TIQM to be consistent with the
Afshar experiment, while claiming that the Copenhagen interpretation
and the many-worlds interpretation are not.[3]"
[3] ^ A Farewell to Copenhagen?, by John Cramer. Analog, December 2005.

Feynman used waves coming back from the future to solve his Quantum
Electrodynamics QED, the most experimentally accurate physics theory
extant, which in my mind lends TIQM credence. Such teteological
effects are expanded on for living systems in Terrence Deacon's book
"Incomplete Nature: How Mind Emerged from Matter".


I don't see how Cramer's interpretation make disappear the terms of the superposition, it is only a post selection for which Everett can provide the
epistemology.

The many world is a direct consequence of linearity of evolution, and
linearity of the tensor product.

(I don't pretend the MWI solves all conceptual problems of QM, note).



And does Afshar's experiment negate MWI? QM?


I have not studied the details of Afshar's experiment, nor so much think about it, so I can't say. I doubt it can negate MWI, or QM, or comp, as the MW idea, like the everything idea, seems compelling at the start, and rather
"natural" to me.

Feel free to present the argument if you have studied it and find it
compelling.

Bruno



On Wed, Oct 24, 2012 at 7:31 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:


On 23 Oct 2012, at 14:50, Roger Clough wrote:

Hi meekerdb

There are a number of theories to explain the collapse of the quantum
wave
function
(see below).

1) In subjective theories, the collapse is attributed
to consciousness (presumably of the intent or decision to make
a measurement).


This leads to ... solipsism. See the work of Abner Shimony.




2) In objective or decoherence theories, some physical
event (such as using a probe to make a measurement)
in itself causes decoherence of the wave function. To me,
this is the simplest and most sensible answer (Occam's Razor).


This is inconsistent with quantum mechanics. It forces some devices into
NOT
obeying QM.




3) There is also the many-worlds interpretation, in which collapse
of the wave is avoided by creating an entire universe.
This sounds like overkill to me.


This is just the result of applying QM to the couple "observer +
observed".
It is the literal reading of QM.




So I vote for decoherence of the wave by a probe.


You have to abandon QM, then, and not just QM, but comp too (which can
only
please you, I guess).

Bruno


http://iridia.ulb.ac.be/~marchal/



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