Single-quantum interferometry: which-way versus which-phase information stored in an ancillary quantum system

• Published in: Journal of physics. A, Mathematical and theoretical Vol. 52; no. 40; pp. 405307 - 405317
• Main Authors: Khademi, Soroush, Reza Bahrampour, Ali
• Format: Journal Article
• Language: English
• Published: IOP Publishing 04.10.2019
• Subjects: accessible information; complementarity; quantum erasure; wave-particle duality
• ISSN: 1751-8113; 1751-8121
• DOI: 10.1088/1751-8121/ab3a1d

In interferometers, the more information about a quantum's path that is available in an ancillary quantum system (AQS), the less visibility the interference has. By use of Shannon entropy, we try to compare the amount of which-phase information with the amount of which-way information stored in the AQS of two-path interferometers with symmetric beam merging. We show that the former is less than or equal to the latter if the bipartite system of the single quantum and the AQS is initially prepared in a pure state and the interaction between the two parts is unitary. The equality holds when symmetry exists. No which-way information is obtained by the measurement that we use for extracting the which-phase information and vice versa. In order to verify the results experimentally, we propose assembling a new single-photon interferometer.