Abstract

The balanced homodyne detector has made possible the detection of squeezed states of light. The essential feature of this detector is that it allows measurement of an arbitrary linear combination of the canonically conjugate observables of the electromagnetic field. We show that it is precisely this feature of the detector which provides a means for studying EPR nonlocality and Bell's inequality. A simple physical statement of this is that a homodyne detector is to its signal field as a Stern-Gerlach magnet is to a spin. Thus a pair of homodyne detectors can be used in the same manner as the magnets in Bohm’s gedanken experiment for studying the EPR question. The quantum mechanical state which demonstrates a violation of Bell's inequality in this system has correlations between the modes entering the two homodyne detectors. It should be noted that this correlation is not between the polarizations of the modes, as in all past EPR experiments using light, rather it is between the occupation numbers of the two modes.

© 1987 Optical Society of America