Photon Bunching

Under photon bunching (of English Bunch - accumulation ) is defined as the occurrence of temporal correlations of single photons from the same source, usually a thermal light source. Figuratively speaking, " clump " photons thermally generated, two detectors measure with increased probability of simultaneous photons from the source.

Photon bunching was first observed by Robert Hanbury Brown and Richard Twiss and is therefore also known as Hanbury Brown Twiss effect ( HBT effect).

History

The initial interest of Hanbury Brown and Twiss was the measurement of the apparent size of stars in the years 1955-56. They presented to two photomultipliers at a variable distance d (up to about 180 m) and measured the spatial correlation of light from a star that fell on both detectors. Due to conceptual difficulties, such as the spatially separated quantum statistical processes in the two detectors could be correlated with each other, they decided to test the experimental setup in the laboratory. In the laboratory then the temporal correlation of the light of a mercury lamp was measured, which has been split by a half-silvered mirror into two beams. Further details of the HBT experiment can be found in Intensitätsinterferometer.

Overview

It can be shown that, for photon bunching of the second order correlation function

Is greater than 1. 111 The term second-order correlation suggests attention to the fact that the intensity is already the product of two wave functions, and this is therefore not a two-point function, but a four-point function.

The variance is generally for the photon bunching greater than for the Poisson distribution, it is therefore also called super- Poisson statistics.

The role of photons can be taken from any other boson, thermally distributed bosonic atoms at extremely low temperatures also show bunching. The tendency of bosons to clump into packets is an important part of the theory of Bose -Einstein condensates.

Comparison with other statistics

With a coherent laser light source, the detection timings of the Poisson distribution, and is followed for all τ. The first explanation of this difference yielded Roy J. Glauber, who was honored for his contributions to quantum theory of optical coherence in 2005 with the Nobel Prize for Physics.

Photon antibunching with contrast only occurs when the time between the photon, a time interval is (for example, in the single-photon source ), and a quantum effect. It usually occurs with sub- Poisson statistics.