Re: Do 2 laser beams interfere?

ilper@xxxxxx wrote:
I read that one electron interferes with himself.
Now I wonder do the wave functions of two electrons interfere.
Practically it's easier to formulate and check it for photons so the
questions is formulated for lasers.

Certainly two laser beams can interfere with each other. Here are references to several experiments that use this to put an upper limit on the anisotropy of the speed of light:

# Cialdea, Lett. Nuovo Cimento 4 (1972), pg 821.
Uses two multi-mode lasers mounted on a rotating table to look for variations in their interference pattern as the table is rotated. Places an upper limit on any one-way anisotropy of 0.9 m/s.

# A. Brillet and J.L. Hall, “Improved Laser Test of the Isotropy of Space”, Phys. Rev. Lett. 42 549–552 (1979).
This is one of the most accurate limits on any anisotropy in the round-trip speed of light in a laboratory. They measured the beat-frequency between a single-mode laser on a rotating table and a single-mode laser fixed to the earth to put a limit on such an anisotropy of 3 parts in 10^15. Due to the construction of their rotating laser, this can also be interpreted as a limit on any anisotropy of space. This is a round-trip experiment because of their use of a Fabry-Perot etalon to determine the frequency of the rotating laser. Note that their limit on the round-trip anisotropy corresponds to a round-trip speed of less than 0.000001 m/s (!); in terms of the more usual one-way anisotropy it is 30 m/s.


Tom Roberts

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