An interference experiment with signal photons from two parametric down-converters, based on the process of induced coherence without induced emission, has been performed. A low-Q optical cavity provides a possible time delay for the idlers. Whether the idler photon is to be delayed or not then determines whether the signal photon behaves like a wave and exhibits interference or behaves like a particle.

• Received 3 May 1993

DOI:https://doi.org/10.1103/PhysRevA.48.4793