Investigation of nonclassical and nonlocal effects in fourth-order optical interference

In this thesis we investigate theoretically and experimentally the phenomena of fourth-order interference, in which the coincidence rate for two-photon detection exhibits a modulation as the optical path changes. We find that, in order to understand these phenomena in terms of photons, Dirac's famous statement on photon interference needs to be modified. We also study the related nonlocal effects of quantum theory.; The predictors relating to fourth-order interference are different for quantum theory and for classical wave theory. The visibility of fourth-order interference can not exceed 50% for classical wave theory, but may reach 100% in quantum theory. We derive a necessary condition and a sufficient condition on two interfering fields for the classical limit to be violated. The process of spontaneous parametric down-conversion produces two highly correlated light fields that satisfy these conditions, and we demonstrate the existence of nonclassical fourth-order interference with these fields.; With the technique of fourth-order interference we are able to measure time intervals between two photons of order a few fsec and to develop a new method for determining the second-order coherence time of an optical field.; We describe a new form of fourth-order interference called spatial beating, in which the beat note is displayed in the space domain. We demonstrate spatial beating by using both down-converted quantum fields and blue and green classical fields with detectors that are about {dollar}10sp5{dollar} times slower than the beat oscillation.; The down-converted photon pair carriers information about the phase and the coherence time of the pump field. The latter can be much longer than the coherence time of each down-converted field. This property of down-conversion and the nature of quantum entanglement are demonstrated in three experiments.; Some fourth-order interference phenomena also violate locality, indicating the nonlocality of quantum theory. We investigate hidden variable theory and the related Bell inequality problem as it relates to fourth-order interference. This leads us to derive a Bell inequality for position variables. We also examine Bell's inequalities for phase and polarization variables. In a two-photon polarization correlation experiment with down-converted light, we demonstrate violation of both Bell's inequality and classical probability.