ADAPTIVE PHASE MEASUREMENTS OF OPTICAL MODES - GOING BEYOND THE MARGINAL Q-DISTRIBUTION

In standard single-shot measurements of the phase of an optical mode, the phase and amplitude quadratures are jointly measured, and the latt er information discarded. These techniques are consequently suboptimal . Here I suggest an adaptive scheme, whereby the phase is estimated fr om the results so far and fed back to control the phase of the local o scillator so as to measure the (estimated) phase quadrature only. I sh ow that adaptive phase measurements can approach optimal phase measure ments for states with both low and high mean photon numbers.