# Polarizing vs nonpolarizing beamsplitter qm toy problems etc

• vzn
In summary: I don't know if he ever got around to running them but I have not seen any published results. Certainly no one has ever published anything to refute the results, so that says a lot about the legitimacy of those criticisms.In summary, there are some classicalist proponents, including established scientist Jaynes, who have criticized the classic Grangier,Roger,Aspect (GRA) photon anticorrelation experiment for using a polarizing beamsplitter. However, these experiments have been repeated and the results have been consistently in line with the original findings, effectively rejecting the classical viewpoint. Jaynes has suggested using circularly polarized light, but this has not been done and does not change the fact that the classical viewpoint has been rejected by these
vzn
hi all .. I have heard of 3 semiclassicalist proponents,
one of them the established scientist Jaynes, criticize the classic
Grangier,Roger,Aspect (GRA) photon anticorrelation
experiment on the grounds
that it used a polarizing beamsplitter. actually, to be more
specific, (rumor is, at a conference)
Jaynes suggested to Grangier redoing the experiment with circularly
polarized light, which has apparently never been done.

my question: how does QM formalism handle the difference
between a polarizing and "nonpolarizing" beamsplitter?
how does it show up in the mathematics? how does it
change the prediction?

along these lines I was thinking it would be neat to develop
a procedure similar to what is done for electronics components
in intro EE classes & intro textbooks. in these classes, you are given all the
laws for each circuit component & the general principles
for writing equations for their interconnections (based roughly
on F=ma), eg Kierkoff's law.

& then apply it by analyzing/solving for
the whole circuit given in diagram.
this procedure can achieve a high degree of sophistication with
eg links between imaginary number operations & solving
the differential eqns for A/C circuits. the components are
resistors, capacitors, etc.

something similar is done in intro physics classes, with little
toy problems of pendulums, blocks, springs, friction, etc. using F=ma,
conservation of energy, etc

it would be neat to see this done by someone for "toy"/"idealized"
QM elements seen in typical QM papers.
I have never seen this done anywhere. seems one could get quite a bit
of mileage out of it. & also very useful/effective in teaching QM.

(some of these diagrams may be on the web but I can't find one
after a quick google search..maybe will post it later in thread if one
turns up)

refs

[1] excellent online description of the GRA experiment by hans devries
http://chaos.swarthmore.edu/courses/phys6_2004/QM/17_EPR_Bell_Details.pdf

[2] recent undergraduate level GRA experiment, online also, by Thorn et al
http://marcus.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf

tx

vzn

http://groups.yahoo.com/group/qm2/

Last edited by a moderator:
vzn said:
hi all .. I have heard of 3 semiclassicalist proponents,
one of them the established scientist Jaynes, criticize the classic
Grangier,Roger,Aspect (GRA) photon anticorrelation
experiment on the grounds
that it used a polarizing beamsplitter.

Grangier and especially Aspect have been through the ringer from the diehard Local Realist/Classicist crowd over the years. Nothing has been too minor to criticize. The fact is, there will ALWAYS be a few who reject the published results for one reason or another. However, these experiments have evolved substantially over the years and have been repeated plenty of times, always yielding the same results as Grangier and Aspect originally presented. They are as accepted as any experiment and meet scientific standards.

Jaynes can say whatever he likes about circular polarized light, that does not change the fact that the classical viewpoint has been clearly rejected. The reason these experiements are picked on is because they shut the door on that viewpoint so tightly.

If someone thinks there is a experiment that proves QM is wrong, well, let's see it. Grangier has indicated those experiments he feels are worth running.

The difference between a polarizing and nonpolarizing beamsplitter in QM formalism can be seen in the mathematics through the use of the Jones matrix. The Jones matrix is a 2x2 matrix that describes the polarization state of a beam of light as it passes through an optical element such as a beamsplitter. In the case of a polarizing beamsplitter, the Jones matrix has a specific orientation that only allows light of a certain polarization to pass through, while reflecting light of the opposite polarization. In contrast, a nonpolarizing beamsplitter has a Jones matrix that allows light of all polarizations to pass through with equal probability.

This difference in the Jones matrix can change the prediction of the experiment, as it affects the probability of the photons being split or not split by the beamsplitter. In the GRA experiment, using a polarizing beamsplitter resulted in a correlation between the polarization states of the two photons, while using a nonpolarizing beamsplitter would have resulted in no correlation.

Developing a procedure for analyzing "toy" QM elements in a similar way to how it is done for electronic components in introductory classes could be a useful tool for understanding QM concepts. It could also be effective in teaching QM, as it would provide a visual representation of the principles and equations involved in QM problems.

References [1] and [2] provided in the post offer excellent explanations and examples of the use of the Jones matrix and its effects on the polarization states of light passing through optical elements. It would be interesting to see this approach applied to other QM experiments and concepts.

## What is a polarizing beamsplitter?

A polarizing beamsplitter is an optical device that divides a beam of light into two beams with different polarizations. It transmits one polarization while reflecting the other, allowing for the separation and manipulation of polarized light.

## How does a polarizing beamsplitter work?

A polarizing beamsplitter works by using a thin layer of material, such as a polarizing film or a coated prism, that selectively transmits or reflects light based on its polarization. This allows for the separation of polarized light into two beams with different polarizations.

## What is the difference between a polarizing and nonpolarizing beamsplitter?

A polarizing beamsplitter selectively transmits or reflects light based on its polarization, while a nonpolarizing beamsplitter evenly splits the light without regard to polarization. This means that a polarizing beamsplitter can separate polarized light into two beams, while a nonpolarizing beamsplitter will not affect the polarization of the light.

## How are polarizing beamsplitters used in quantum mechanics?

Polarizing beamsplitters are commonly used in experiments and devices related to quantum mechanics, such as quantum computing and quantum cryptography. They allow for the manipulation and measurement of polarized light, which is often used to encode and transmit quantum information.

## What are some common toy problems involving polarizing and nonpolarizing beamsplitters?

Some common toy problems involving polarizing and nonpolarizing beamsplitters include using them to create interference patterns, studying the effects of polarized light on different materials, and using them to demonstrate concepts such as superposition and entanglement in quantum mechanics.