Squeezed light

In physics, a squeezed coherent state is any state of the quantum mechanical Hilbert space such that the uncertainty principle is saturated. That is, the product of the corresponding two operators takes on its minimum value:

The simplest such state is the ground state ${\displaystyle |0\rangle }$ of the quantum harmonic oscillator. The next simple class of states that satisfies this identity are the family of coherent states ${\displaystyle |\alpha \rangle }$.

Often, the term squeezed state is used for any such state with ${\displaystyle \Delta x\neq \Delta p}$ in "natural oscillator units". The idea behind this is that the circle denoting a coherent state in a quadrature diagram (see below) has been "squeezed" to an ellipse of the same area.

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