DCQE - Why don't we get idler pattern?

[San K]

In the delayed choice quantum eraser such as one described in the Kim paper...

http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraserWe have five detectors D0, D1, D2, D3, D4 and D5

The signal photon strikes the detector D0.

Please note this discussion is more focussed on the idler and not the signal photon.

The idler strikes one of four remaining detectors (D1, D2, D3, D4, D5) each time it goes through the apparatus/experiment.

Can we get the interference pattern of the idler at each of the four detectors?

What would the pattern look like? (after removing "noise" via pairing of each idler with signal via the co incidence counter)

Why not? I might have missed some part of the experiment, that I don't understand.

 

[eljose79]

Hello,

Thank you for your question. I am happy to provide some insight on the delayed choice quantum eraser experiment and the questions you have raised.

In the delayed choice quantum eraser experiment, the goal is to observe the interference pattern of the idler photon at each of the four detectors (D1, D2, D3, D4, D5) after it has passed through the apparatus. However, this is not always possible due to the nature of quantum mechanics and the concept of wave-particle duality.

First, let's understand the setup of the experiment. The signal photon is sent through a double-slit apparatus, which creates an interference pattern on the screen behind it. The idler photon is also sent through the same apparatus, but its path is split into two by a beam splitter. One path leads to the detectors D1-D4, while the other path leads to detector D5. The detectors are set up in a way that they can either detect the presence of the photon or not, but they cannot distinguish between which path the photon took.

Now, when the signal photon strikes detector D0, it is entangled with the idler photon. This means that the state of the signal photon is linked to the state of the idler photon. If we were to measure the state of the signal photon, we could determine which path the idler photon took, and therefore, we would not observe an interference pattern at the detectors D1-D4.

However, in the delayed choice quantum eraser experiment, the state of the signal photon is not measured until after the idler photon has passed through the apparatus and reached one of the detectors. This means that the path of the idler photon is not determined until after it has passed through the apparatus.

Now, to answer your question, can we get the interference pattern of the idler at each of the four detectors? The answer is yes, but it depends on the setup of the experiment. If we do not measure the state of the signal photon, then we can observe an interference pattern at the detectors D1-D4. However, if we do measure the state of the signal photon, then we will not observe an interference pattern at the detectors D1-D4.

What would the pattern look like? The interference pattern would be similar to the pattern observed at the double-slit apparatus when only the signal photon was sent through. It would be a series of light and dark