Abstract
Pairs of 826.8-nm correlated photons, generated by parametrically down-converting 413.4-nm krypton-ion laser light, are directed into a single Mach-Zehnder interferometer such that each photon of the pair enters a different input port. The rate of coincidence at the two output ports displays oscillations (as the path-length difference is swept) with a spatial period equal to the 413-nm wavelength of the pump photons, and with a visibility of 62% when the path-length difference exceeds the coherence length of the individual photon beams. This unequivocally demonstrates the nonclassical and entangled nature of the two-photon state.
- Received 16 May 1990
DOI:https://doi.org/10.1103/PhysRevLett.65.1348
©1990 American Physical Society