In quantum physics, the **squeeze operator** for a single mode of the electromagnetic field is

where the operators inside the exponential are the ladder operators. Its action on the annihilation operator produces (for simplicity we use )

with and .

The squeeze operator is ubiquitous in quantum optics and can operate on any state. For example, when acting upon the vacuum, the squeezing operator produces the squeezed vacuum state.

The squeezing operator can also act on coherent states and produce squeezed coherent states. The squeezing operator does not commute with the displacement operator:

nor does it commute with the ladder operators, so one must pay close attention to how the operators are used.

Application of both operators above on the vacuum produces squeezed states:

- .

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### Famous quotes containing the word squeeze:

“We will get everything out of her that you can *squeeze* out of a lemon and a bit more.... I will *squeeze* her until you can hear the pips squeak.”

—Eric, Sir Geddes (1875–1937)