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Phys. Rev. Lett. 89, 133602 (2002) [4 pages]

Adaptive Homodyne Measurement of Optical Phase

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Michael A. Armen*, John K. Au, John K. Stockton, Andrew C. Doherty, and Hideo Mabuchi
Norman Bridge Laboratory of Physics 12-33, CaliforniaInstitute of Technology, Pasadena, California 91125

Received 1 April 2002; published 4 September 2002

We present an experimental demonstration of the power of feedbackin quantum metrology, confirming the predicted [ H. M. Wiseman Phys. Rev. Lett. 75 4587 (1995)] superior performanceof an adaptive homodyne technique for single-shotmeasurement of optical phase. For measurements performed on weak coherentstates with no prior knowledge of the signal phase, adaptive homodyneestimation approaches closer to the intrinsic quantum uncertaintythan any previous technique. Our results underscore the importanceof real-time feedback for reaching quantum limits in measurement andcontrol.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.133602
DOI:
10.1103/PhysRevLett.89.133602
PACS:
42.50.Dv, 03.65.Ta, 03.67.–a, 06.90.+v

*Electronic address: armen@caltech.edu