Delayed-choice test of quantum complementarity with interfering single photons

Phys Rev Lett. 2008 Jun 6;100(22):220402. doi: 10.1103/PhysRevLett.100.220402. Epub 2008 Jun 3.

Abstract

We report an experimental test of quantum complementarity with single-photon pulses sent into a Mach-Zehnder interferometer with an output beam splitter of adjustable reflection coefficient R. In addition, the experiment is realized in Wheeler's delayed-choice regime. Each randomly set value of R allows us to observe interference with visibility V and to obtain incomplete which-path information characterized by the distinguishability parameter D. Measured values of V and D are found to fulfill the complementarity relation V2+D2 < or =1.