Adaptive quantum measurements of a continuously varying phase

Abstract

The quantum-limited estimation of stochastically varying phase of a continuous beam of the electromagnetic field was analyzed. Both nonadaptive and adaptive measurements, and dyne detection (using a local oscillator) and interferometric detection were considered. For the case of dyne detection, a coherent beam resulted with phase invariance≅N-1/2/2, which was √2 times smaller than that achieved by nonadaptive detection. For a squeezed beam, variance scaling was N-2/3 compared to N-1/2 for heterodyne detection. © Oxford University Press 2002.