The elusive Heisenberg limit in quantum-enhanced metrology

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NATURE COMMUNICATIONS | ARTICLE OPEN

The elusive Heisenberg limit in quantum-enhanced metrology

Nature Communications 3 , Article number : 1063 doi:10.1038/ncomms2067

Received 16 April 2012  –  Accepted 14 August 2012  - Published 18 September 2012

Abstract

Quantum precision enhancement is of fundamental importance for the development of advanced metrological optical experiments, such as gravitational wave detection and frequency calibration with atomic clocks. Precision in these experiments is strongly limited by the 1/√N shot noise factor with N being the number of probes (photons, atoms) employed in the experiment. Quantum theory provides tools to overcome the bound by using entangled probes. In an idealized scenario this gives rise to the Heisenberg scaling of precision 1/N. Here we show that when decoherence is taken into account, the maximal possible quantum enhancement in the asymptotic limit of infinite N amounts generically to a constant factor rather than quadratic improvement. We provide efficient and intuitive tools for deriving the bounds based on the geometry of quantum channels and semi-definite programming. We apply these tools to derive bounds for models of decoherence relevant for metrological applications including: depolarization, dephasing, spontaneous emission and photon loss.

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The elusive Heisenberg limit in quantum-enhanced metrology : Nature Communications : Nature Publishing Group.

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Rafał Demkowicz-Dobrzański, Jan Kołodyński, & Mădălin Guţă (2012).
The elusive Heisenberg limit in quantum-enhanced metrology

NATURE COMMUNICATIONS, 3 (1063) DOI: 10.1038/ncomms2067

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