Entanglement-free Heisenberg-limited phase estimation

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Title Entanglement-free Heisenberg-limited phase estimation
Author Higgins, Brendon Lloyd; Berry, D. W.; Bartlett, S. D.; Wiseman, Howard Mark; Pryde, Geoff
Journal Name Nature
Year Published 2007
Place of publication England
Publisher Nature Publishing Group
Abstract Measurement underpins all quantitative science. A key example is the measurement of optical phase, used in length metrology and many other applications. Advances in precision measurement have consistently led to important scientific discoveries. At the fundamental level, measurement precision is limited by the number N of quantum resources (such as photons) that are used. Standard measurement schemes, using each resource independently, lead to a phase uncertainty that scales as 1/ffiNffiffiffi p —known as the standard quantum limit. However, it has long been conjectured1,2 that it should be possible to achieve a precision limited only by the Heisenberg uncertainty principle, dramatically improving the scaling to 1/N (ref. 3). It is commonly thought that achieving this improvement requires the use of exotic quantum entangled states, such as the NOON state4,5. These states are extremely difficult to generate. Measurement schemes with counted photons or ions have been performed with N#6 (refs 6–15), but few have surpassed the standard quantum limit12,14 and none have shown Heisenberg-limited scaling. Here we demonstrate experimentally a Heisenberg-limited phase estimation procedure. We replace entangled input states with multiple applications of the phase shift on unentangled single-photon states. We generalize Kitaev's phase estimation algorithm16 using adaptive measurement theory17–20 to achieve a standard deviation scaling at the Heisenberg limit. For the largest number of resources used (N5378), we estimate an unknown phase with a variance more than 10 dB below the standard quantum limit; achieving this variance would require more than 4,000 resources using standard interferometry. Our results represent a drastic reduction in the complexity of achieving quantum-enhanced measurement precision.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.nature.com/nature/index.html
Alternative URI http://dx.doi.org/10.1038/nature06257
Copyright Statement Copyright 2007 Nature Publishing Group. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
Volume 450
Issue Number 7168
Page from 393
Page to 397
ISSN 0028-0836
Date Accessioned 2008-01-22
Language en_AU
Research Centre Centre for Quantum Dynamics
Faculty Faculty of Science, Environment, Engineering and Technology
Subject PRE2009-Quantum Optics and Lasers
URI http://hdl.handle.net/10072/17413
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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