OPERATIONAL THEORY OF 8-PORT HOMODYNE DETECTION

The eight-port homodyne detection apparatus is analysed in the framewo rk of the operational theory of quantum measurement. For an arbitrary quantum noise leaking through the unused port of the beam splitter, th e positive operator valued measure and the corresponding operational h omodyne observables are derived. It is shown that such an eight-port h omodyne device can be used to construct the operational quantum trigon ometry of an optical field. The quantum trigonometry and the correspon ding phase space Wigner functions are derived for a signal field probe d by a classical local oscillator and a squeezed vacuum in the unused port.