Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.14/42233
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- Title
- Adaptive quantum measurements of a continuously varying phase
- Related
- Physical review A, Vol. 65, Issue 4, p.043803-1-043803-11
- DOI
- 10.1103/PhysRevA.65.043803
- Publisher
- American Physical Society
- Date
- 2002
- Author/Creator
- Berry, D. W
- Author/Creator
- Wiseman, H. M
- Description
- We 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 nonadaptive and adaptive measurements, and both dyne detection (using a local oscillator) and interferometric detection. We take the phase variation to be φ = √κξ(t), where ξ(t) is δ-correlated Gaussian noise. For a beam of power P, the important dimensionless parameter is N = Pℏωκ, 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 ≃ N⁻¹/²/2. This is √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.
- Description
- 11 page(s)
- Resource Type
- journal article
- Organisation
- Macquarie University. Dept. of Physics
- Identifier
- http://hdl.handle.net/1959.14/42233
- Identifier
- ISSN:1050-2947
- Identifier
- mq-rm-2002016715
- Language
- eng
- Rights
- Copyright 2002 by The American Physical Society. Reprinted from Physical review A.
- Full Text
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