Talk:Mach–Zehnder interferometer

Are there always two detectors in a Mach-Zender? I'm pretty. You only really need one, perhaps depending on the application. -- DrBob 17:03, 7 Apr 2004 (UTC)

According to Optics, Hecht, 4th edition, you need only one. I currently don't have time to rewrite the article though. -- Gerritholl 08:58, 20 Sep 2004 (UTC)

Don't phase shifts only occur during reflection off a material with higher n and never during refraction? If so then there are fewer phase shifts than the article states in the last paragraph. Chad 11/8/2005

There is a phase shift of pi upon reflection on a medium with higher index of refraktion, as you say. There is also never a phase shift caused by the process of refraction itself (off the top of my head, this wouldn't be compatible with the boundary conditions of the fields, but this might be entirely wrong). I think what the author means in this case is a difference in phase compared to what the light would have, had it traversed the same path in vacuum. Basically, the optical path length difference $$n_{glass}x-n_{air}x$$ -- Osquar F 9 Oct 2006


 * I think a full quantum description of the action of the Mach-Zehnder interferometer should be added in the main article. Danko Georgiev MD 12:27, 23 January 2007 (UTC)

This article is sloppy and lacks a bit of rigor. These interferometers are not just used for interrogation of samples but also for distance ranging and some other applications. A Michelson interferometer is a Mach-Zehner interferometer which has been folded upon itself. Also note that Michelson interferometers do have two output ports, the second is where light is reflected back towards the source. I'll delete this comment in the article and add some more stuff in the next few weeks when I have some time. Fincle (talk) 14:58, 4 February 2010 (UTC)
 * I agree that this article needs more rigor. Is there a flag that we can set to help it get picked up by one of the clean-up projects? Cavebear42 (talk) 01:41, 13 March 2013 (UTC)

What is a Mach-Zender modulator ? --68.0.120.35 20:26, 17 April 2007 (UTC)

With what probability photon reach detector A in right down picture ( http://en.wikipedia.org/wiki/Image:Interferometre_de_Mach-Zender_paradoxe.svg ) ?

This article should be compared to the one on Fabry Perot interferometers. That one has the math worked out and this one is more conceptual. I would imagine the articles would want to be written in a similar form. 136.152.177.188 (talk) 20:40, 30 April 2010 (UTC)

The drawing, http://en.wikipedia.org/wiki/File:Interferometre_de_Mach-Zender_paradoxe.svg, should be corrected or omitted; the probabilities are not legible. --Ryan Westafer (talk) 22:44, 14 July 2010 (UTC)
 * I'd have to agree here. The (very large) picture at the end doesn't seem to fit into the article at all and lacks explanation.  It should either be expanded or removed. Cavebear42 (talk) 01:41, 13 March 2013 (UTC)


 * I did some cleanup work on the article. I added figures, and modified and provided an explanation for the figure that you found did not fit in. I would appreciate further suggestions for improvement. Thanks! Stigmatella aurantiaca (talk) 12:18, 19 March 2013 (UTC)

Suggestions for improvement
Here are some points I noticed when reading the article, which might help improving it further: These are of course just suggestions, some points might be not so important and there might be room for improvement elsewhere. I hope it helps anyway. &mdash;&thinsp; H HHIPPO  12:11, 14 April 2013 (UTC)
 * 1) General
 * 2) Avoid excessive use of "we". In parts this looks a bit like textbook style, did anybody check for copypaste problems?
 * 3) A phase is an angle, not a (wave)length. For example, a phase shift of π corresponds to half a wavelength, but it is π.
 * 4) Bulleted lists are nice where they make sense, but having a bullet in front of each paragraph doesn't help much.
 * 5) Topics that could be covered/expanded if material is found
 * 6) Other types of beams (electrons, atoms?)
 * 7) Other, not so fundamental applications?
 * 8) History
 * 9) Lede
 * Is a bit shaky ("the two beams caused by a sample"?). Could be longer, could use a short introduction for non-experts.
 * 1) Introduction
 * 2) Start out explaining what it is and how it works, not with specific details (maybe re-arrange with material from the Set-up section). Introduce concepts like appearance of fringes or test cell before using them.
 * 3) "Note also the precise orientation of the beam splitters." No, I don't, how should I? What's precise about it?
 * 4) "when an extended source is used" or when the beam is expanded, like in the figure.
 * 5) Figure 1: The text would fit better in the main article. "we imagine" ??
 * 6) Figure 2: I don't get what that's saying.
 * 7) What is a "well behaved response"?
 * 8) How it works
 * 9) Find a more encyclopedic section title
 * 10) The beam splitters don't have to be half-silvered, dielectric ones are mentioned later
 * 11) One detector can be enough
 * 12) The second bullet point in set-up is hard to understand
 * 13) In "Caveat": it's not clear which paths are equal or not and what energy conservation has to do with it.

Suggestion for improvement
The section on Counterfactual measurement should be corrected. The question in the text and the caption of Figure 4 is ill-posed. There is nothing paradoxical about photons moving along the upper path being evenly detected by A and B when the lower path is interrupted. — Preceding unsigned comment added by 187.112.59.69 (talk) 16:51, 1 June 2013 (UTC)

Counterfactual measurement chapter
Could someone explain what is counterfactual or paradox about this experiment. It has the same simple classical explanation as a double slit where one slit is closed. Mirror M blocks one wave, so there is no (destructive) interference at A anymore, so A can measure photons again. DParlevliet (talk) 20:47, 24 February 2014 (UTC)


 * Consider the Elitzur–Vaidman bomb tester. Through straightforward modifications of the illustrated apparatus, it is possible to achieve arbitrarily close to 100% efficiency distinguishing between live and dud bombs, without photons ever being absorbed by live bombs setting them off. Does classical wave mechanics predict anything remotely comparable to this scenario, which involves measuring the properties of the bombs without any interactions with photons? Stigmatella aurantiaca (talk) 02:52, 25 February 2014 (UTC)


 * The bomb tester is a another paragraph. I asked about the "Counterfactual measurement". DParlevliet (talk) 19:56, 25 February 2014 (UTC)
 * They are very closely related. Stigmatella aurantiaca (talk) 21:12, 25 February 2014 (UTC)

QM version
In my opinion, it's a necessity to have 2 input-ports in this version. No input is equivalent to the vacuum. No vacuum, no QM.

nonlocalized fringe pattern
The article talks about localized and nonlocalized fringe patterns, but what does that mean? A fringe pattern is shown in eg the flame images in the article. Is it localized? nonlocalized? What would change if it were the other kind? Johnjbarton (talk) 16:51, 18 August 2023 (UTC)