Hidden variables - Bell - The Law of Malus?

In summary, the conversation discusses the use of Bell's Theorem to show the incompatibility of EPR hidden variables with QM. However, the speaker suggests that a simple application of Malus' Law can also accomplish this. They give an example of vertically polarized photons passing through a polarized lens rotated at 30°, showing that only 1/4 of the photons pass through both the R30° and L30° filters. This refutes the idea of hidden variables, but the speaker also mentions the need for something like Bell's Theorem to refute local realism. They then realize their mistake in their previous reasoning, as a tagged photon is no longer vertically polarized after passing through the R30° filter.
  • #1
Zafa Pi
631
132
Invariably in the lay literature when it comes time to show that EPR hidden variables are incompatible with QM, Bell's Theorem is invoked (e.g. Greene's "Fabric of the Cosmos", Zeilinger's "Dance of the Photons", Rosenblum's "Quantum Enigma", ...).

I don't see why a simple application of Malus' Law (old as the hills) doesn't accomplish it, to wit:
If we have a zillion vertically polarized photons beamed into a polarized lens whose axis is rotated 30° to the right of vertical (R30°), then about 3/4 get thru. So that 3/4 have been tagged (hidden) with the instruction to pass thru R30°. The same goes for L30°. Thus at least 1/2 of the zillion have been tagged to go thru both. But Malus tells us that only 1/4 go thru both.

I haven't found a thread that mentions this. Nor do I see why this doesn't refute hidden variables.
Admittedly to refute local realism one seems to need something like Bell's Theorem with entangled pairs.
 
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  • #2
I'm sorry I didn't think this thru. Once a tagged photon passes thru R30° it's no longer vertically polarized so there is no tag for L30°.
 

Related to Hidden variables - Bell - The Law of Malus?

1. What are hidden variables and how do they relate to Bell's Theorem?

Hidden variables refer to theoretical properties or characteristics of a system that are not directly observable. Bell's Theorem is a mathematical proof that demonstrates the incompatibility of local hidden variable theories with quantum mechanics.

2. What is the significance of Bell's Theorem in the field of quantum mechanics?

Bell's Theorem is significant because it shows that the predictions of quantum mechanics cannot be explained by local hidden variable theories. This challenges our understanding of reality and the fundamental principles of causality and determinism.

3. How does the Law of Malus relate to Bell's Theorem?

The Law of Malus is a formula that describes the intensity of light after passing through a polarizing filter. It is used in Bell's Theorem to demonstrate the correlation between measurements of particle spin in different directions, which cannot be explained by local hidden variable theories.

4. Can Bell's Theorem be tested experimentally?

Yes, Bell's Theorem has been tested and confirmed through various experiments. These experiments involve measuring the correlations between the spin of entangled particles in different directions, and comparing them to the predictions of local hidden variable theories.

5. What implications does Bell's Theorem have for our understanding of reality?

Bell's Theorem challenges the classical notion of causality and determinism, suggesting that there may be non-local influences at play in the quantum world. It also raises questions about the nature of reality and the limitations of our current understanding of the universe.

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