Importance of Hanbury Brown and Twiss experiment

[qnach]

I read Hanbury Brown and Twiss's experiment is using one beam but split into two to test their correlation.
It said the traditional correlation test were using two beams........
This confused me, sorry.

All the correlation tests I learnt such as Stern-Gerlash are using one beam? (Sorry if I am wrong)
I was also told traditional interferometers are concerning about amplitude but Hanbury Brown and Twiss were concerning about intensity?
Isn't the square of amplitude is the intensity?

Please advice me where did I made mistake?

 

[PeterDonis]

Stern-Gerlash

A single Stern-Gerlach experiment is not a "correlation experiment". To do a correlation experiment with Stern-Gerlach devices, you need two such devices, each of which measures one of two entangled particles. Just as in the Hanbury-Brown-Twiss effect, you need two detectors, not one.

 

[PeterDonis]

I read Hanbury Brown and Twiss's experiment is using one beam but split into two to test their correlation.

I was also told traditional interferometers are concerning about amplitude but Hanbury Brown and Twiss were concerning about intensity?

It would help if you would give specific references for where you read or were told these things.

 

[PeterDonis]

using one beam but split into two to test their correlation

Yes. You have one light beam coming from a source, which is split by a beam splitter, and then you have two detectors, and you look for correlations between the detections. The correlations give you information about the light source.

 

[qnach]

This is the Michelson-Morley interferometery I know of. Is it one source or two sources?

 

[qnach]

This is the Mach-Zender interferometer I know of. Is it one source or two sources?

 

[qnach]

It would help if you would give specific references for where you read or were told these things.

OK. Here is an example that saying HBT measures intensity
https://physicstoday.aip.org/news/glauber-hall-and-hansch-share-the-2005-nobel-prize-in-physics
on page 19 (the first page of that article) upper-right corner.....
the Hanbury Brown–Twiss (HBT) apparatus measured the correlation in the intensities ....

 

[WernerQH]

Have a look at https://en.wikipedia.org/wiki/Hanbury_Brown_and_Twiss_effect

The effect seemed puzzling at the time, because of Dirac's remark that "a photon only interferes with itself" in his textbook. But E.Purcell showed that the HBT effect can also be understood classically:
E. Purcell (1956). "The Question of Correlation Between Photons in Coherent Light Rays". Nature. 178 (4548): 1449–1450.
(from the Wikipedia page)

 

[qnach]

A single Stern-Gerlach experiment is not a "correlation experiment". To do a correlation experiment with Stern-Gerlach devices, you need two such devices, each of which measures one of two entangled particles. Just as in the Hanbury-Brown-Twiss effect, you need two detectors, not one.

OK Stern-Glash is not (Sorry I am very confused). It is not even an interferometry. But how about Michelson-Morley and Mach-Zehnder?

 

[qnach]

Have a look at https://en.wikipedia.org/wiki/Hanbury_Brown_and_Twiss_effect

The effect seemed puzzling at the time, because of Dirac's remark that "a photon only interferes with itself" in his textbook. But E.Purcell showed that the HBT effect can also be understood classically:
E. Purcell (1956). "The Question of Correlation Between Photons in Coherent Light Rays". Nature. 178 (4548): 1449–1450.
(from the Wikipedia page)

I tried to obtain this paper https://www.nature.com/articles/1781449a0
But why has it no title as you said "The Question of Correlation Between Photons in Coherent Light Rays"

 

[WernerQH]

I tried to obtain this paper https://www.nature.com/articles/1781449a0
But why has it no title as you said "The Question of Correlation Between Photons in Coherent Light Rays"

I just copied the wikipedia reference, and it seems to point to a nature paper with that title. Unfortunately it's behind a paywall. Have your read the wikipedia page?

 

[PeterDonis]

This is the Michelson-Morley interferometery I know of. Is it one source or two sources?

This is the Mach-Zender interferometer I know of. Is it one source or two sources?

Both of them have one source, which gets split by a beam splitter into two beams. Just as I described in post #4.

 

[PeterDonis]

Stern-Glash is not (Sorry I am very confused). It is not even an interferometry.

Correct.

But how about Michelson-Morley and Mach-Zehnder?

Both of them are interferometers, yes. What gets observed at any detector depends on the relative amplitude and phase of the beams.

In the HBT effect, by contrast, what gets observed at each detector depends only on the intensity of the beam coming to that detector.

 

[Cthugha]

OK Stern-Glash is not (Sorry I am very confused). It is not even an interferometry. But how about Michelson-Morley and Mach-Zehnder?

Michelson interferometers, Mach-Zehnder interferometers (and also the double slit) measure field correlations. The quantity you measure in the end is of course an intensity (because this is how detectors work), but you delay or offset one field in space or time and quantify the correlation between the fields. Loosely speaking, the information you get is: If I know the value of my field at some time and some position, how well can I predict the value of the field at a temporal delay t' and a position offset x'. This is entirely classical information and cannot be used to identify nonclassical states.

In HBT, the question you ask is: If I detect one photon from my light field at one detector, what is the normalized probability to detect another photon at the other detector? This information may tell you something about whether a state is nonclassical. Take for example the simple example of a single-photon state. If the photon gets detected at the first detector, it is gone and you will never find a simultaneous detection at the second detector. A Michelson interferometer cannot give you that kind of information.