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A lot of books explain the first order and second order coherence correlations for light. They explain the difference between these using interferometers (Michelson and Hanbury-Brown and Twiss (HBT) interferometer). However, it is odd none of the books mention the essential difference between the two interferometers. I just want to be sure that the difference between the two techniques is that, Michelson has one detector and HBT has two detectors?

Michelson interferes the light and then detects while HBT detects light at different detectors and then checks the correlation.

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    $\begingroup$ Yes, that's pretty much it. Michaelson measures amplitude correlations, but HBT detects the light ... and measures intensity ... and then looks for correlations as the path length changes. $\endgroup$ – garyp Apr 20 '16 at 16:49
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Hanbury Brown and Twiss effect is the correlation between intensities measured simultaneously by independent detectors. It was first used with radio astronomy, and after Twiss provided the mathematics for the quantum optical theory, it was applied to light.

Thus there are two ways to make stellar interferometers, the first by means of classical electromagnetic theory, due to Michelson; and the second due to quantum optical effects, due to Hanbury-Brown and Twiss.

The Michelson interferometer brings together light for the interference experiments; the HBT correlator depends upon the correlation of intensity measured simultaneously at two different locations.

Both methods require a variation of the effective distance between the light collectors. For the Michelson interferometer this distance is limited by the size of the reflector, and the rigidity and stability of the mechanical supports for the mirrors used to bring the separate light beams together.

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  • $\begingroup$ Hi, I know what you mentioned here, but it does not clear my doubt as mentioned in the question. $\endgroup$ – Chetan Waghela May 10 '16 at 17:33
  • $\begingroup$ @ChetanWaghela: I've spelled out the differences more carefully. $\endgroup$ – Peter Diehr May 10 '16 at 21:57
  • $\begingroup$ "The Michelson interferometer brings together light for the interference experiments; the HBT correlator depends upon the correlation of intensity measured simultaneously at two different locations." Lets, twist the question a bit, I am asking why is the HBT Correlator known as intensity interferometer, and Michelson a Amplitude interferometer? Do all Intensity interferometers have two detectors spatially separated? $\endgroup$ – Chetan Waghela May 14 '16 at 16:53
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    $\begingroup$ @ChetanWaghelach: your last mentioned supposition is correct. $\endgroup$ – Peter Diehr Apr 22 '18 at 23:34

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