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March 01, 2005

Class review — 3/1/2005

Hey Class,

Note that there is no pre-flight for Thursday. I want to get the pre-flights and the classes synchronized. Also, there was a problem with the example that I gave regarding Rabi oscillations in the presence of a T1-type process. I will clear that up next class. And, the lecture notes from today need some cleaning up; they will probably not be posted before Thursday.

Today we talked about:

  1. We reviewed the equations of motion for the density matrix and Bloch vector from last class.

  2. We considered a T2-type process in a Ramsey experiment. With a fluctuating magnetic field present during the free-evolution time, decoherence results from an ensemble measurement. Note that decoherence is showing up with only pure Hamiltonian evolution. With T2-type decoherence present, the coherences decay exponentially in time.

  3. We started talking about light, and all of the ways that light can interact with an atom. Only two of these processes (plain Rabi oscillations and stimulted Raman transitions) can be explained semi-classically (quantum atom but classical field). You can't get spontaneous emission without quantizing the electro-magnetic field.

  4. We laid out a cheesy (mmm...cheese) classical model where light is an oscillating electric field driving an electron that is bound harmonically to the nucleas. The electron will only be driven strongly when the electric field oscillates at the resonance frequency, and when the electron moves it will radiate!

Cheers,

Brian

Posted by Brian at March 1, 2005 04:08 PM

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