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Does getting which-way info introduce a phase difference?

  1. Mar 20, 2012 #1
    does getting which-way info introduce a phase difference (or cause de-coherence) between both the "waves"?

    and does erasure of which-way information restore coherence?
    Last edited: Mar 20, 2012
  2. jcsd
  3. Mar 21, 2012 #2
    a difference from what?

    the 'which-way' information completely changes the state, like the slits be 1 and 2, then you have 1+2 without any information, then 1 OR 2 with information
    you can't phase change your way between (1+2),(1),(2)
  4. Mar 21, 2012 #3
    forgot to mention, sorry.....

    phase difference between two entangled photons (two-photon interference)
  5. Mar 22, 2012 #4
    Which way information usually referes to dual-slit type experiments, there's only one photon there at any one time so there is no enganglement.
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