# quantum field description of squeezing

Following with a series of questions regarding quantum squeezing, let me add another one: quantum squeezing of vacuum is a real propagating state of the field, it can be switched on and off, squeezing can be altered and information can be sent modulating it. So, there must be real degrees of freedom in the QED field description that account for the squeezing. But squeezing does not affect the field itself, but the associated uncertainties. The electromagnetic quantum field is usually described as quantum oscillators over a wavenumber $k$ and a polarization number (either -1 or 1).

so the question is: where are the degrees of freedom that describe a squeezed field? are they simply missing?

This question follows up discussion from these questions: here and here

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Please define quantum squeezing of vacuum... As it stands, your question frankly sounds gibberish. Can you make everything more clear? Maybe a formula or two? –  Chris Gerig Jul 26 '12 at 18:45

The squeezed states at time $t$ are created from the vacuum by multiplication with a unitary matrix $e^{iX(t)}$ where $X(t)$ is an appropriate Hermitian expression quadratic in the creation and annihilation operators in momentum space, with coefficients depending on the time $t$.