The entire history of a photon

In their 2013 experimental paper Danan, Farfunki, Bar-Ad, and Vaidman conducted a spectroscopical experiment proposed by Vaidman.

They have observed a lack of certain frequencies related to vibration of mirrors in an interferometer, which was interpreted as an evidence for discountinuous trajectories of light. This point of view was widely debated and advocated. With elementary calculations I show that it is completely natural to have this features of the power spectrum missing. Moreover, I pinpoint additional effects allowing to distinguish the two-state vector formalism from traditional quantum mechanics by the power of their prediction. At the end of talk I will explain the Gilbert algorithm and how can it be used as a general method of recognizing entanglement in any few-body system.