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What is polarization in the language of photons and QM?

  1. Mar 31, 2006 #1
    I know what polarization is in classical EM. But what is polarization in the language of photons and QM? I am thinking that it's something to do with spin.
  2. jcsd
  3. Mar 31, 2006 #2
    It is said that two eigenstates of spin correspond to two kinds of circularly polarized states, but I don't know the details too.

    Anyone knows what subject deals with this stuff?

    Thank u!
  4. Mar 31, 2006 #3

    Meir Achuz

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    Photon polarization is usually described in terms of helicity, which can be
    +1 or -1 for a photon. The helicity +1 state correspond to Left circular polarization and the -1 to Right circular polarization. A plane polarized photon is the same linear combination of circular polarizations as in Classical EM. The reason H=+1 corrsponds to LH circular polarization is that particle physicsts use a z=axis in the direction the photon is moving, while the classical circular polarization is how the E vector rotates as you look toward the oncoming photon.
  5. Apr 8, 2006 #4
    I still want to know how helicity is related to polarization.
    Can you recommend some readings?

    Thank you!
  6. Apr 9, 2006 #5
    Well, they are not directly related in terms of a formula because both concepts come from different "places" in physics. Polarization comes from EM and helicity is a QM concept since you need the concept of SPIN to define helicity. You do not need spin to define polarization.

    Polarization can be defined for both materials (local fluctuations in the electronic density that lead to dipoles or quadrupoles) as well as EM waves

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