Quantum amplifier

In physics, a quantum amplifier is an amplifier that uses quantum mechanical methods to amplify a signal; examples include the active elements of lasers and optical amplifiers.

The main figures of merit of a quantum amplifier are its gain and added noise. These parameters are not independent. In a linear amplifier, the higher the gain, the higher the added noise. In lasers, the added noise corresponds to the amplified spontaneous emission of the active medium. The unavoidable noise of quantum amplifiers is one of the reasons for the use of digital signals in optical communications and can be deduced from the fundamentals of quantum mechanics.

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