Quantum optical coherence: From linear to nonlinear interferometers

Interference between two waves is fundamentally driven by the coherence, an intrinsic property of waves. The classical coherence of two fields then defines the degree of first-order coherence, as quantified by their cross-correlation function. Here, we study the coherence properties of various interferometer configurations, spanning from linear over semi-nonlinear to fully nonlinear settings [1] – [3] .