A. Gilchrist et al., CONTRADICTION OF QUANTUM-MECHANICS WITH LOCAL HIDDEN-VARIABLES FOR QUADRATURE PHASE-AMPLITUDE MEASUREMENTS, Physical review letters, 80(15), 1998, pp. 3169-3172
We demonstrate a contradiction of quantum mechanics with local hidden
variable theories for continuous quadrature phase amplitude (''positio
n'' and ''momentum'') measurements. For any quantum state, this contra
diction is lost for situations where the quadrature phase amplitude re
sults are always macroscopically distinct. We show that for optical re
alizations of this experiment, where one uses homodyne detection techn
iques to perform the quadrature phase amplitude measurement, one has a
n amplification prior to detection, so that macroscopic fields are inc
ident on photodiode detectors. The high efficiencies of such detectors
may open a way for a loophole-free test of local hidden variable theo
ries.