The fully quantum description of the two path interference a single photon in Mach–Zehnder interferometer is presented. interaction-free delayed-choice scenario proposed to test interference. Several schemes arrangements designed realize are considered.

Interferometers are widely used as sensors in precision measurement. Compared with a conventional Mach–Zehnder interferometer, the sensitivity of correlation-enhanced nonlinear interferometer can break standard quantum limit. Phase plays significant role enhanced performance. In this paper, we review improvement phase estimation technologies interferometers, including SU(1,1) and SU(1,1)-SU(2) ...