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Why the formula (it is the density operator in its initial state) below has this form?

  1. May 26, 2015 #1
    Screen Shot 2015-05-25 at 3.01.31 PM.png a
    In the formula above, on the left hand side, ρ(0) is a system's density operator in its initial state. a is the annihilator operator of the system, and a+ is the create operator of the system. ρss is the system's density operator in its steady state.

    But I don't understand why this formula writes in this way. Could anyone tell me what is the physics behind this formula?

    Many thanks!
     
  2. jcsd
  3. May 27, 2015 #2

    naima

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    Gold Member

    A link would help!
     
  4. May 28, 2015 #3

    naima

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    Gold Member

    Maybe an idea:
    http://en.wikipedia.org/wiki/POVM#Post-measurement_state

    It looks like the result of the density matrix after a POVM measurement on your steady state. You get it as a post measurement result at t = 0. If it is not an eigen value of the hamiltonian, it evolves in time.
     
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