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Abstract

In this Letter, the quantum correlation measurement technique as a method of
power noise monitoring is investigated. Its principal idea of correlating two
photodetector signals is introduced and contrasted to the conventional
approach, which uses only a single photodetector. We discuss how this scheme
can be used to obtain power noise information below the shot noise of the
detected beam and also below the electronic dark noise of the individual
photodetectors, both of which is not possible with the conventional approach.
Furthermore, experimental results are presented, that demonstrate a detection
of technical laser power noise one order of magnitude below the shot noise of
the detected beam.