Delayed-choice quantum eraser experiment

In summary, the conversation discussed the concept of quantum erasing and its effects on interference patterns. It was suggested that applying the eraser to all the entangled photons would not change anything, and the behavior of the photons could be explained within the classical causal order. However, there is still confusion and debate on this topic, and further research is needed. The conversation also mentioned an interesting article on the matter and provided a link to the author's blog for more information.
  • #1
gtorassa
6
1
TL;DR Summary
A specific configuration of delayed-choice quantum eraser experiment where the eraser involves all the photons (not just a part of them)
In the Kim's experiments (see picture below) part of the downwards photons are involved in a quantum eraser and part aren't.

1567414560458.png


In D0 (upward path) we see interference if the entangled photons (downward path) are detected in D1 or D2 and we don't see interference if the entangled photons are detected in D3 or D4.
Taking into account all the photons, in D0 we don't see any interference.
But what happens in D0 if we apply the eraser to all the entangled photons going downwards?
If we see interference (due to the eraser) it means that the behaviour in D0 depends on what happens in the future, if we don't see any interference it means that the eraser doesn't work.
 
Physics news on Phys.org
  • #2
Thanks for bringing up this quantum erasing experiment, I'm ruminating on it as well.

As I understand it, if we apply the eraser to all the entangled photons, i.e. eliminate beamsplitters BSa and BSb, nothing would change: To each photon detected at detector D1 (D2) correlates a fringe-photon (anti-fringe photon) at D0. The function of D3 and D4 is only that to show that as long we have information on the which-way then interference disappears.

As to the 'back from the future' action that's where I got stuck too. But I'm very skeptic. For such strong statements I would like to see equally strong evidence. I believe one can recast the observed phenomenon within the classical causal order. But, admittedly, I have to clarify myself on this. If I may add my two cents... My guess is that if someone replaces D1 and D2 with a screen (or CCD or step motor readout) one would see the fringe- and anti-fringe interference pattern. The photons have orthogonal polarization, say vertical (V) and horizontal (H). The system behaves as if, when photons come from slit A with V pol. and from slit B with H pol. they always hit one detector and produce one type of fringe, whereas when polarization is inverted (photons from slit A with H pol. and from slit B with V pol.) then they always hit the other detector producing the other fringe type. However, that would imply that some sort of destructive (constructive) interference occurs at BSc always to allow the photons hit only D1 (D2) for the two different situations. How this can be I don't know, in fact that could be completely wrong, but seems to me the only way one can save classical causality.
 
  • #3
I'm not thinking about eliminating the BSa and BSb beamsplitters, I'm thinking about creating two identical paths:

1567426841227.png


Do we see interference?
 
  • #4
But with this you have also eliminated the quantum erasing part. That is, you can trace back the which-way and therefore both detectors will show no interference fringes.

Edit: Thinking on this further (was perhaps too hasty with my answer) I'm no longer sure. In fact how can we establish the which-way with this setup? Only by inserting again a detector on the path. Ok, I'm confused , should perhaps delete this post, just keep it for those who have already read... :rolleyes:
 
  • #5
:smile: don't worry, I'm confused too :wink:.
I have been thinking about this problem for some months but I cannot solve it
 
  • #6
gtorassa said:
:smile: don't worry, I'm confused too :wink:.
I have been thinking about this problem for some months but I cannot solve it
You might find this interesting.

https://arxiv.org/abs/1905.03137
 
  • Like
Likes gtorassa, vanhees71 and Aidyan
  • #7
Mentz114 said:
You might find this interesting.

https://arxiv.org/abs/1905.03137

Thanks. This article seems to be precisely what I was looking for. Will go through it. Kastner has also many other similar articles on the matter. She seems to work a lot on the transactional interpretation of QM. Her blog might give more insights: https://transactionalinterpretation.org/
 

1. What is the delayed-choice quantum eraser experiment?

The delayed-choice quantum eraser experiment is a thought experiment in quantum physics that tests the principle of wave-particle duality. It involves the use of a double-slit experiment and a delayed-choice setup, where the decision to observe or not observe the particle's path is made after it has already passed through the slits.

2. How does the delayed-choice quantum eraser experiment work?

In the experiment, a photon is fired through a double-slit apparatus, creating an interference pattern on a screen. A second apparatus, called a quantum eraser, is then used to determine which slit the photon passed through. However, the decision to use the quantum eraser is delayed until after the photon has already passed through the slits. This allows researchers to observe the effects of retrocausality, where the future choice of measurement can affect the past behavior of the particle.

3. What is the significance of the delayed-choice quantum eraser experiment?

The experiment challenges our understanding of causality and the nature of reality. It suggests that the behavior of particles is not determined until they are measured, and that the future can influence the past. This has implications for our understanding of time and the concept of free will.

4. What are the potential applications of the delayed-choice quantum eraser experiment?

The experiment has implications for quantum computing and cryptography, as well as for understanding the quantum nature of time and causality. It could also have practical applications in developing new technologies, such as quantum sensors and communication devices.

5. What are some current debates and controversies surrounding the delayed-choice quantum eraser experiment?

Some researchers argue that the results of the experiment can be explained through classical physics and do not necessarily require a quantum interpretation. There is also debate over the implications of the experiment for our understanding of causality and the nature of reality. Additionally, the delayed-choice quantum eraser experiment has sparked philosophical discussions about the role of consciousness in quantum mechanics.

Similar threads

Replies
3
Views
1K
Replies
2
Views
687
Replies
8
Views
900
  • Quantum Physics
Replies
1
Views
778
Replies
1
Views
636
Replies
19
Views
951
Replies
9
Views
1K
Replies
4
Views
805
  • Quantum Physics
Replies
2
Views
269
  • Quantum Physics
Replies
2
Views
939
Back
Top