Delayed choice quantum eraser – Yoon Vs Walborn experiment/paper is it true that in the Walborn experiment we manipulate p, but in Yoon paper we do not? The below link discusses the Walborn paper: http://grad.physics.sunysb.edu/~amarch/ s = s-photon, p = p-photon s-photon is going down and detected by detector Ds p-photon is going up and detected by detector Dp The delay (path length) for p is such that s is detected at Ds well before p reaches the polarizer. Case 1: The polarizer/eraser is kept there and the experiment is repeated same way for say a million photons (sent one by one) Case 2: The polarizer/eraser is removed AFTER s is detected at Ds (and before p reaches the polarizer) and the same sequence of events is repeated same way for say a million photons (sent one by one) Questions: a) Will the pattern in case 1 (after correlating the entangled pairs and removing noise) be that of an interference pattern? b) Will the pattern in case 2 1 (after correlating the entangled pairs and removing noise) be that of a non- interference pattern? c) In case 2 (or even case 1) when s arrives a. its position is marked? On the screen of Ds b. However we do not know which one is the real s till we correlate with p? (i.e. remove noise) c. Why can we not figure out s simply via timing (velocity, distance, time calculation), without having to correlate with p? d) Case 2 is interesting because this is different from the experiment by Yoon where we do not mess with p? Yoon paper is discussed on http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser In the Yoon paper the path of p is not “controlled” ….hence when s strikes Ds, one could conclude that the path of p has been fixed (probabilistically) at the time struck Ds. However the Walborn paper is different -- where we still play with P (after s has struck Ds) by keeping or removing the polarizer/eraser. Thus Yoon-kim = DCQE with p allowed to follow whatever path it will take Walborn = DCQE with manipulation of p? Yoon = one could still conclude that once s is detected, the path of p is fixed ("probabilistically") Walborn = we are "operating" on p after s is detected, thus s that has happened in the past is showing results that correlate with p that is (being manipulated) in future?