ABSTRACT
Here the angle θ , and hence the measured quadrature, is determined by the phase of the local oscillator. This quadrature is reminiscent of the product of the field amplitude and the cosineof thephase, cos(φ−θ), and indeed“measuredphaseoperators”havebeendefined in terms of these (Barnett and Pegg 1986 Paper 1.7). The quadratures are not phase operators, of course, but measuring them can provide a very good approximation to measurement of the phase (Vaccaro and Pegg 1994c Paper 5.2). Homodyne detection can also provide something close to a single-shot measurement of the phase by actively adjusting the local oscillator phase as the photocurrent is measured (Wiseman 1995 Paper 5.3). The idea is to use the accumulated photocurrent data, up to any instant during the measurement, to determine the new value selected for the local oscillator phase.
