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Do all which-way attempts/techniques introduce phase difference between the waves ?

  1. Jun 24, 2011 #1
    do all which-way attempts/techniques introduce phase difference between the "waves"?

    In a double slit experiment

    One hypothesis (or fairly well accepted theory?) is:

    If we try to find which-way via Quarter Wave Plates (QWPs), we add a phase difference (between the "waves that seems to have traveled" from each slit).

    The phase difference results in the waves not being coherent which in turn spoils/distorts the interference pattern.

    Interference pattern is the (neatest and) cleanest when the waves are coherent.

    Even in the (modified) Mach–Zehnder experiments, attempts to get which-way cause phase difference between the "waves that seem to travel" both the arms simultaneously.

    Are there any alternate techniques/methods (other than QWPs) to get which-way without causing any phase difference in the "waves that seem to travel" both/numerous paths?

    Wheeler had as a very hypothetical/thought-experiment, suggested telescopes. But I guess telescopes cannot be used.

    Also can we ever observe/detect a photon (position, spin etc) without disturbing it?
    Last edited: Jun 24, 2011
  2. jcsd
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