M. Koashi et al., PROBING THE 2-PHOTON PHASE COHERENCE OF PARAMETRICALLY DOWN-CONVERTEDPHOTONS BY A LOCAL OSCILLATOR, Physical review. A, 50(5), 1994, pp. 180003605-180003608
A degenerate beam of down-converted photon pairs from a nonlinear crys
tal pumped by pulsed light was mixed with coherent local oscillator pu
lses by a beam splitter, and the coincidence rate for detections of ph
otons at the two output beams was measured. The coincidence rate showe
d interference fringes as the phase difference between the pump light
and the local oscillator was varied. It showed a negative correlation
in some range of the phase difference.