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Quantum logic gate measurement?

  1. Nov 13, 2008 #1
    Do quantum logic gates perform measurements? (collapse the wavefunction)

    For example:

    If I apply a cNOT gate to a pair of cubits with wavefunction 1/[tex]\sqrt{2}[/tex] |10> + 1/[tex]\sqrt{2}[/tex] |00>
    what would I expect as the result?

    1/[tex]\sqrt{2}[/tex] |11> + 1/[tex]\sqrt{2}[/tex] |00>
    ?

    or

    1|11>
    or
    1|00>

    or
    are the states not entangled? This seems unlikely because it would be cloning...
     
  2. jcsd
  3. Nov 13, 2008 #2
    A logic gate is unitary, a measurement (when described as including the collapse) is not unitary. So, the result of the cnot is 1/[tex]\sqrt{2}[/tex] |11> + 1/[tex]\sqrt{2}[/tex] |00>. And yes, this is an entangled state.
     
  4. Nov 14, 2008 #3
    Thank you,
    That's what seemed the most reasonable, but I wasn't sure.
     
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