Polarization Eraser & Entanglement

DrChinese
Science Advisor
Homework Helper
Gold Member
Messages
8,498
Reaction score
2,128
Following Fig. 1 in the following paper:

Eberly (2002): Bell inequalities and quantum mechanics

In an ideal case (this is far from easy to do): Send an incident beam from one side of entangled photon pairs into a beamsplitter, and then recombine the outputs back into a single stream. Let's call the outputs of the beamsplitter as X and Y, where X and Y are orthogonal. The theory is that the recombined stream X+Y will still evidence entanglement, as the polarization has been erased.

In the next step, let's do the same thing for both Alice and Bob. You end up with 4 outputs from the 2 beamsplitters, which are before erasure:

Alice X
Alice Y
Bob X
Bob Y

1. So if you take the recombined streams (Alice X + Alice Y) and (Bob X + Bob Y), they are still entangled. As far as I know, this experiment (as described by Eberly in more complex versions) has not been performed. Does anyone know of a reference on this?

2. Here is a strange one: Alice X and Bob X are identical streams, as are Alice Y and Bob Y. I believe that theory would say that (Alice X + Bob Y) and (Bob X + Alice Y), if they could be combined, would be entangled! Were that true, it would indicate that the probability waves are "real" even though the observable properties apparently are not. Any thoughts? Has anyone seen anything on this?
 

Attachments

  • PolarizationEraser.jpg
    PolarizationEraser.jpg
    6.1 KB · Views: 517
Physics news on Phys.org
Probably no one has bothered with experiment described by Eberly because his derivation is erroneous as explained by Ryff here http://arxiv.org/pdf/0902.1724"
 
Last edited by a moderator:
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!
Back
Top