reproduce the classical result: if the photons are replaced by identical fermions such as electrons, the antisymmetry of wave functions under exchange of particles renders the interference destructive, leading to zero joint detection probability for small detector separations. This effect is referred to as antibunching of fermions [Henny, 1999]. The above treatment also explains photon antibunching [Kimble, 1977]: if the source consists of a single atom, which can only emit one photon at a time, simultaneous detection in two closely spaced detectors is clearly impossible. Antibunching, whether of bosons or of fermions, has no classical wave analog. From the point of view of the field of quantum optics, the HBT effect was important to lead physicists (among them Roy J. Glauber and Leonard Mandel) to apply quantum electrodynamics to new situations, many of which had never been experimentally studied, and in which classical and quantum predictions differ. See also Bose–Einstein correlations Degree of coherence Timeline of electromagnetism and classical optics References Note that Hanbury Brown is not hyphenated. – paper which (incorrectly) disputed the existence of the Hanbury Brown and Twiss effect – experimental demonstration of the effect download as PDF download as PDF – the cavity-QED equivalent for Kimble & Mandel's free-space demonstration of photon antibunching in resonance fluorescence External links http://adsabs.harvard.edu//full/seri/JApA./0015//0000015.000.html http://physicsweb.org/articles/world/15/10/6/1 https://web.archive.org/web/20070609114114/http://www.du.edu/~jcalvert/astro/starsiz.htm http://www.2physics.com/2010/11/hanbury-brown-and-twiss-interferometry.html Hanbury-Brown-Twiss Experiment (Becker & Hickl GmbH, web page) Quantum optics