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I have recently come across two key concepts in quantum optics: shot noise and back-action noise. This is very important for me to know: first, are shot noise and back-action noise the same? Please let me know if there is any other equivalent term for back-action noise among the quantum optics community. I am also wondering whether back-action is the nature of light beam in vacuum, or is it related basically to measurement detector like homodyne?

I really like to know exclusively the characteristics of back-action noise to be able to model it.

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Back action noise and shot noise both arise from the discrete nature of quantum mechanics, but they are not the same. In a quantum optical system shot noise is the noise due to counting photons at the output of the detector while back action noise is due to the photons imparting momentum to the mirrors in the system. Both arise from the statistical nature of quantum mechanics. There are some optical configurations which avoid back-action noise (back-action evading) such as the Sagnac interferometer, but shot noise cannot be avoided without using non-classical states of light.

The first chapter of this thesis out of the LIGO collaboration has a nice introduction to quantum noise in a simple Michelson interferometer which is sensitive to both types of quantum noise.

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