Complementarity and quantum erasure in two simple which-path detection systems

Abstract

We theoretically consider the complementarity in two "which-path" detection systems. The possibility of delayed choice via the action of quantum erasure in a system is considered with respect to the complementarity, as well. The first system considered is a Mach-Zehnder interferometer coupled with a side interferometer by using an optical Kerr media in a common arm which is used to get "which-path" information via a quantum nondemolition measurement of a signal photon. The second system is composed of a Mach-Zehnder interferometer coupled with a coincidence detection system in which a pair of generated biphotons travels and is incident on a two-level absorber for coincidence detection via a two-photon process. Both arms of the coincidence detector system include optical Kerr crystals, one of which is coupled with the Mach-Zehnder interferometer. In those interferometer systems, the loss of the "which-path" information causes a revival of the interference pattern as Wheeler and Scully supported in their delayed-choice experimental system and quantum erasure experimental system.