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Heterodyning Single-Photon Pairs.

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Final rept. 1 Apr 93-31 Dec 95,

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We have obtained theoretical and experimental second- and fourth-order interference patterns for entangled photons of different colors entering single and dual Mach-Zehnder interferometers MZIs in which dispersive elements have been deliberately placed. Entangled-photon pairs are a form of nonclassical light. We have observed the interference of entangled photons of different colors, in both second- and fourth-order, using coincidence detection, by sweeping the path-length difference in an interferometer or two spatially separated interferometers. The entangled photons are created by pumping a KDP parametric-downconverter crystal with a krypton-ion laser beam at 413 nm, creating photon pairs with center wavelengths in the vicinity of 830 nm. The coherence properties and photon statistics of this nonclassical source of light were determined. Although photon wavepackets are generally broadened, as well as delayed, by passage through dispersive optical elements, coincidence measurements made with entangled photon pairs can be free of such broadening This occurs for materials with particular dispersive behavior, as well as when the dispersion is balanced in both arms. This nonlocal behavior arises from the entanglement in the frequencies of the downconverted pair photons. We have shown that pump-frequency oscillations are present in the coincidence rate patterns for arbitrarily long path-length-difference times, confirming the robustness of this nonlocal phenomenon in the presence of dispersion. The difference-frequency oscillations, which correspond to heterodyning single-photon pairs, are also robust in the presence of dispersion, though they decay for large path-length-differences. Potential areas of applicability of twin photon beams range from photonics to visual science to computer science.

Subject Categories:

  • Nuclear Physics and Elementary Particle Physics
  • Electricity and Magnetism
  • Optics
  • Radiofrequency Wave Propagation

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