Question about a modified delayed choice quantum eraser. 2nd order interference?

In summary, the delayed choice quantum eraser experiment has been modified to eliminate any time delay or choice, and the resulting setup raises questions about interference and the role of which-path information. Further research is needed to fully understand this modified version.
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OK, a quick intro to the delayed choice quantum eraser is at wikipedia (http://en.wikipedia.org/wiki/Delayed...quantum_eraser [Broken]). I have attached a figure of the modified DCQE. In this setup there is no delay, there is no choice, and there is recombination of the idlers instead.
In the modified DCQE the signal beams are identically prepared as that in the DCQE. But the idler beams are prepared differently from the DCQE. Whereas in the DCQE the idlers are subject to either of detection or recombination, in the modified DCQE the idlers are definitely combined at an identical optical pathlength from the source, and the pathlength of the idlers is also identical to the pathlength of the signals. So all four optical paths to the two detectors from the source differ by no more than a coherence length(of the signal and idler).
In this preparation do the detectors display interference(simple second order indistinguishability interference with pathlength difference/phase)? Of course you could get a fourth order coincidence effect, but do you also get second order interference at each detector? (much like in the ZWM 1991 expt of Mandel et. all)
If an attenuator is placed in the upper idler pathway, in which case the distinguishing “which-path” information is implied, then is the interference at both detectors is negated?
 

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Hello, thank you for sharing this interesting setup with us. The delayed choice quantum eraser experiment is a well-known and puzzling experiment in the field of quantum mechanics. Your modified version raises some intriguing questions.

Firstly, in your setup, the idler beams are prepared differently compared to the original DCQE. This means that the idlers are always combined at an identical optical pathlength from the source, and this pathlength is also identical to the pathlength of the signals. This is an important modification, as it eliminates the possibility of any time delay or choice in the experiment. This also ensures that the four optical paths to the two detectors differ by no more than a coherence length.

In this preparation, it is possible that the detectors may display interference. This would be a second-order interference, similar to what was observed in the ZWM 1991 experiment by Mandel et al. However, it is important to note that the presence of an attenuator in the upper idler pathway would imply which-path information, and this could negate the interference at both detectors. This is because the which-path information would lead to a collapse of the quantum state, resulting in a loss of interference. This is a well-known phenomenon in quantum mechanics, and it has been observed in various experiments.

In conclusion, your modified DCQE setup is an interesting variation of the original experiment, and it raises some intriguing questions about interference and the role of which-path information. Further research and experiments would be needed to fully understand the implications of this modified setup. Thank you for bringing this to our attention.
 

1. What is a modified delayed choice quantum eraser?

A modified delayed choice quantum eraser is an experiment that tests the principles of quantum mechanics, specifically the idea of wave-particle duality. It involves observing the behavior of photons (particles of light) as they pass through a series of slits and detectors, and then manipulating the data post-detection to see if the photons behaved as waves or particles.

2. How is this experiment different from a traditional delayed choice quantum eraser?

In a traditional delayed choice quantum eraser, the decision to measure the photons as particles or waves is made after they have already passed through the slits and detectors. In a modified delayed choice quantum eraser, the decision is made before the photons are detected, but the data is manipulated after detection to see if the photons behaved as particles or waves.

3. What is 2nd order interference in this experiment?

In this experiment, 2nd order interference refers to the interference pattern observed when photons are measured as waves, even though they were originally detected as particles. This is a phenomenon that can only be explained by the principles of quantum mechanics.

4. What is the significance of this experiment?

This experiment challenges our understanding of the behavior of particles at the quantum level and raises questions about the nature of reality. It also has potential implications for future technologies, such as quantum computing.

5. What are the potential applications of a modified delayed choice quantum eraser?

Aside from furthering our understanding of quantum mechanics, a modified delayed choice quantum eraser could potentially be used for secure communication and data encryption, as well as in the development of more advanced quantum technologies.

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