Phase-dependent which-way information

• Published in: Physics letters. A Vol. 376; no. 46; pp. 3479 - 3484
• Main Authors: Schilling, U., von Zanthier, J.
• Format: Journal Article
• Language: English
• Published: 15-10-2012
• Subjects: Detectors; Interference; Interferometers; Mathematical analysis; Optimization; Phase shift; Recognition; Solid state physics
• ISSN: 0375-9601
• DOI: 10.1016/j.physleta.2012.10.019

We introduce an observable for reading out a which-way detector in a Young-type interferometer whose eigenstates either contain full which-way information or none at all. We calculate the which-way knowledge K that can be retrieved from this observable and find that K depends on the phase difference [d] that the interfering quantum object accumulates on its passage through the interferometer. It turns out that for certain phase shifts K ([d]) equals one, independent of the visibility of the interference pattern. In addition, within a certain range of phase shifts K ([d]) can be larger than the which-way information obtained from the observable recognized to provide optimal which-way information on average.