Abstract

A scheme is proposed for experimentally achieving the famous two-slit gedanken experiment using photons. A particle’s quantum pathways can interfere to produce fringes in the probability for the particle to be found at some location. If the path taken by the particle is experimentally determined, the complementarity principle says that the fringes must disappear. To carry out this experiment with photons is difficult because normally the act of determining a photon’s location destroys it. We propose to overcome this by putting a type-II optical parametric amplifier (OPA) in each arm of a Mach-Zehnder interferometer and observing fringes at the output. An OPA responds to an input photon by increasing its probability to produce a pair of photons, one having polarization orthogonal to the input photon.

© 1991 Optical Society of America