Can the Mach-Zehnder interferometer be used as a which-way detector for photons?

[San K]

can we find which-way in mach-zender? just like we do in double-slit

like the one given below:

http://en.wikipedia.org/wiki/Mach%E2%80%93Zehnder_interferometer"

if so, what would the results be similar to double-slit? i.e. the photon will either take upper arm or lower arm path...in a random manner but not behave as if it took both at the same time...

 

[Demystifier]

In MZ the wave takes both paths (it's not a problem for a wave), so it cannot be used for a which-way detector of a wave. But if you think that photon is not a wave but a particle that takes a single path, then you must use a concrete interpretation of QM different from the standard interpretation. The best known interpretation of this kind is the Bohmian one, but in this case the actual trajectory is ˝opposite˝ to the naive classical trajectory.