Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Dipole operator and correlations

  1. Dec 18, 2012 #1

    I am reading a paper (http://arxiv.org/abs/0901.3105), where they after eq. (3) mention something I can't understand. First of all, (3) comes from the master equation of a collection of N atoms in a cavity. They say that (page 2, right after (3)):

    The last term describes the coupling of the atom-field coherence to the collective spin-spin correlations which locks the relative phase between atoms and field to the phase of the macroscopic atomic dipole.

    I don't see why the term [itex]\left\langle {\sigma _1^ + \sigma _2^ - } \right\rangle[/itex] constitutes the dipole correlations between atoms. σ± is a simple transition operator, and I have never heard that it is related to the dipole of a transition.

    I would be grateful to get some help with this.

  2. jcsd
  3. Dec 18, 2012 #2


    User Avatar
    Science Advisor

    I have no idea of laser theory, but I find the last term in eq.3 not too strange. Obviously the expectation of ##\sigma_1^-## will change when a spin is shifted from 2 to 1 which is described by the last term.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook