Quantum behavior experiment flawed?

[tistemfnp]

To observe entanglement you need these two-photon observations!

In SPDC every photon emitted at down conversion frequency is entangled, as this is the principle of SDPC. Photons with the higher frequencies are blocked. Any photon with no coincidence is still entangled, you just didn't catch its partner in the measurement setup. And entangled photons will not show interference as long as you don't fix their partner in a certain position. That should be clear from the cited figure of Dopfer.

Everything said. From my side, I wouldn't know what else to say. Sorry.

 

[vanhees71]

But in Fig. 2 of the Walborn paper

https://doi.org/10.1103/PhysRevA.65.033818

you see interference fringes. How can that be, if your claim is true? Maybe I don't understand which precise setup you are discussing?

You are always referring to Dopfer. Is it about her thesis? Then which of the two experiments in which setup you discuss?

 

[tistemfnp]

you see interference fringes

No you don't. You see statistical coincidence with the other photon of the pair, which is fixed. I am referring to Dopfer, because everyone with minimum optical expertise would immediately catch the situation (including te Walborn situation) looking at the referred figure.

Answering these questions correctly would immediately clarify the situation:
1) What changes can be observed with the "interference pattern" if detector D1 is shifted in x?
2) What would happen when overlapping different "interference patterns" from different experiments where D1 was shifted in x?
3) Is a detector D1 necessary if we use a photoscreen instead of D2?

 

[vanhees71]

Once more: You contradict the observed facts in the paper by Walborn et al.

I cannot discuss your argument about Dopfer, because you don't tell me, which setup you are referring to in her thesis.

(1) In her "Heisenberg microscope experiment", as expected, she gets double-slit interference fringes if the detector $D_1$ is positioned in the focal plane (she reports 97% contrast) while she gets no double-slit interference fringes if $D_1$ is positioned in the image plane. It depends on the setup, whether you see fringes or not. Of course for any position of $D_1$ between these extremes, you get interference fringes with more or less contrast. This indeed needs very basic facts about the opticl properties of lenses and basic Fraunhofer diffraction theory.

(2) Quantum theory discusses results of experiments really done, not results of fictitious experiments. You need to give a detailed description of which experiment you have in mind in this question to discuss it.

(3) I don't know what you mean here either. With a photoscreen you cannot make coincidence meausurements to begin with.

 

[PeterDonis]

Thread closed for moderation.

 

[berkeman]

After a Mentor discussion, the OP is on a 10-day vacation from PF, and this thread will remain closed. Thank you everybody for trying to help the OP.