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March 29, 2005

March 29 — class review;

Hi Class,

Casimir's wife's name was Josina Jonker; they were married in 1933.

Remember! No class on April 5, and the homework is due on April 7.

There is a pre-flight for Thursday.

We got embroiled in a discussion of g(2) at the end of class. Correlation functions are confusing, and I'll bring a concrete example to next class.

Today we talked about:
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  1. Quantum States of light. We talked about Fock, or number, states. For these states, the expectation value of the electric field is 0, but the variance depends on n.

  2. Coherent states. These states are produced by a laser (maybe) and classical currents (an antenna). Coherent states are a specific superposition of number states, where the probability distribution is Poisson-ian in the number state basis. Coherent states are also characterized by a single parameter that is a complex number. The expectation value of the field is finite, and shows classical-like behavior. That means that the electric field strength oscillates in time. What is not classical about coherent states is the extra quantum "fuzz" on the electric field, although the size of the fuzz as a fraction of the electric field strength shrinks as the expectation value of n grows.

  3. We talked about the correlation function g(2) as something that distinguishes Fock from coherent states. More on this next time!

Cheers,

Brian

Posted by Brian at March 29, 2005 04:16 PM

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