Adaptive Quantum Measurements of a Continuously Varying Phase

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dc.creatorBerry, D. W.
dc.creatorWiseman, H. M.
dc.date2001-11-02
dc.date2002-09-19
dc.date.accessioned2026-07-07T06:02:57Z
dc.date.available2026-07-07T06:02:57Z
dc.descriptionWe analyze the problem of quantum-limited estimation of a stochastically varying phase of a continuous beam (rather than a pulse) of the electromagnetic field. We consider both non-adaptive and adaptive measurements, and both dyne detection (using a local oscillator) and interferometric detection. We take the phase variation to be \dotϕ= \sqrtκξ(t), where ξ(t) is δ-correlated Gaussian noise. For a beam of power P, the important dimensionless parameter is N=P/\hbarωκ, the number of photons per coherence time. For the case of dyne detection, both continuous-wave (cw) coherent beams and cw (broadband) squeezed beams are considered. For a coherent beam a simple feedback scheme gives good results, with a phase variance \simeq N^{-1/2}/2. This is \sqrt{2} times smaller than that achievable by nonadaptive (heterodyne) detection. For a squeezed beam a more accurate feedback scheme gives a variance scaling as N^{-2/3}, compared to N^{-1/2} for heterodyne detection. For the case of interferometry only a coherent input into one port is considered. The locally optimal feedback scheme is identified, and it is shown to give a variance scaling as N^{-1/2}. It offers a significant improvement over nonadaptive interferometry only for N of order unity.
dc.description11 pages, 6 figures, journal version
dc.identifierhttps://arxiv.org/abs/quant-ph/0111013
dc.identifierhttp://arxiv.org/abs/quant-ph/0111013
dc.identifierPhys. Rev. A 65, 043803 (2002)
dc.identifierdoi:10.1103/PhysRevA.65.043803
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/89808
dc.subjectQuantum Physics
dc.titleAdaptive Quantum Measurements of a Continuously Varying Phase
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