Reply to "Comment on 'Einstein-Podolsky-Rosen state for space-time variables in a two-photon interference experiment'"

Abstract

The assertion of Kwait, Steinberg, and Chiao [preceding Comment, Phys. Rev. A 48, 3999 (1993)] that alignment problems and the size of the beam-defining irises explain the decrease in the visibility in two-photon interference experiments is examined. We argue that these effects can explain the reason that the visibility does not attain its maximum theoretical value, but that it fails to explain the decrease in the visibility with the path differences in the interferometers. We conclude that one explanation of this effect is the breakdown of perfect frequency phase matching in parametric down-conversion.