2015/10/25 by Giuseppe Argentieri, Janet Anders, Argentieri, Giuseppe +1
Physics and Astronomy · #FOS: Physical sciences #Quantum Physics (quant-ph) #quant-ph
paper · pdf · doi:10.48550/arxiv.1510.07238
arxiv created 2015/10/25 · arxiv updated 2015/10/27
It is well known that the Mach-Zender interferometer exhibits a trade-off between the a priori which-path knowledge and the visibility of its interference pattern. This trade-off is expressed by the inequality P2 + V2 ≤ 1, constraining the predictability P and visibility V of the interferometer. In this paper we extend the Mach-Zender scheme to a setup where the central phase shifter is substituted by a generic unitary operator. We find that the sum P2 + V2 is in general no longer upper bounded by 1, and that there exists a whole class of interferometers such that the full fringe visibility and the full which-way information are not mutually exclusive. We show that P2 + V2 ≤ LU, with 1 ≤ LU ≤ 2, and we illustrate how the tight bound LU depends on the choice of the unitary operation U replacing the central phase shifter.