Using feedback to eliminate back-action in quantum measurements

Wiseman, H. M. (1995) Using feedback to eliminate back-action in quantum measurements. Physical Review A, 51 3: 2459-2468. doi:10.1103/PhysRevA.51.2459

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Author Wiseman, H. M.
Title Using feedback to eliminate back-action in quantum measurements
Journal name Physical Review A   Check publisher's open access policy
ISSN 1050-2947
Publication date 1995
Sub-type Article (original research)
DOI 10.1103/PhysRevA.51.2459
Open Access Status File (Author Post-print)
Volume 51
Issue 3
Start page 2459
End page 2468
Total pages 10
Place of publication College Park, MD, United States
Publisher American Physical Society
Subject 3100 Physics and Astronomy
3107 Atomic and Molecular Physics, and Optics
Abstract A quantum-nondemolition (QND) measurement is one which does not disturb the quantity it measures. Any measurement can be regarded as a QND measurement followed by an additional back-action which may disturb that quantity. By feeding back the measurement result to control the system dynamics, this back-action can always be eliminated in principle. A practical device based on homodyne measurement of the x quadrature of a cavity mode is investigated. First, a χ(2) crystal is inserted in the cavity so that it becomes a degenerate parametric oscillator at threshold. Then the photocurrent is used to control coherent driving of the cavity, so as to give positive feedback with unit gain. This feedback, combined with the nonlinearity, turns the homodyne measurement into a QND measurement of x. The device can also be used to measure the x quadrature of a traveling wave, and gives near-perfect QND correlations over a large bandwidth. However, the quality of the measurement is badly degraded by even slightly inefficient photodetectors.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Mathematics and Physics
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Citation counts: Scopus Citation Count Cited 44 times in Scopus Article | Citations
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