Measuring photon anti-bunching from sideband squeezing with continuous-variable techniques

Photon anti-bunching, or the tendency of photons to be detected apart from one another, is characterized by the second-order coherence function which has previously been measured using discrete-variable (DV) single-photon counting methods. The authors theoretically propose and experimentally demonstrate a continuous-variable (CV) technique for measuring the second-order coherence of quantum states of light at sideband frequencies. The scheme is based on the original Hanbury-Brown-Twiss (HBT) intensity interferometer, but instead uses optical homodyne detection in each arm, to obtain the second-order coherence from a set of quadrature amplitude correlation measurements (each of which can be independently time-averaged).