How to perform the most accurate possible phase measurements

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Title How to perform the most accurate possible phase measurements
Author Berry, D. W.; Higgins, Brendon Lloyd; Bartlett, S. D.; Mitchell, M. W.; Pryde, Geoff; Wiseman, Howard Mark
Journal Name Physical Review A (Atomic, Molecular and Optical Physics)
Year Published 2009
Place of publication USA
Publisher American Physical Society
Abstract We present the theory of how to achieve phase measurements with the minimum possible variance in ways that are readily implementable with current experimental techniques. Measurements whose statistics have high-frequency fringes, such as those obtained from maximally path-entangled (|N,0⟩+|0,N⟩)/√2 (“NOON”) states, have commensurately high information yield (as quantified by the Fisher information). However, this information is also highly ambiguous because it does not distinguish between phases at the same point on different fringes. We provide schemes to eliminate this phase ambiguity in a highly efficient way, providing phase estimates with uncertainty that is within a small constant factor of the Heisenberg limit, the minimum allowed by the laws of quantum mechanics. These techniques apply to NOON state and multipass interferometry, as well as phase measurements in quantum computing. We have reported the experimental implementation of some of these schemes with multipass interferometry elsewhere. Here, we present the theoretical foundation and also present some additional experimental results. There are three key innovations to the theory in this paper. First, we examine the intrinsic phase properties of the sequence of states (in multiple time modes) via the equivalent two-mode state. Second, we identify the key feature of the equivalent state that enables the optimal scaling of the intrinsic phase uncertainty to be obtained. This enables us to identify appropriate combinations of states to use. The remaining difficulty is that the ideal phase measurements to achieve this intrinsic phase uncertainty are often not physically realizable. The third innovation is to solve this problem by using realizable measurements that closely approximate the optimal measurements, enabling the optimal scaling to be preserved. We consider both adaptive and nonadaptive measurement schemes.
Peer Reviewed Yes
Published Yes
Publisher URI http://pra.aps.org/
Alternative URI http://dx.doi.org/10.1103/PhysRevA.80.052114
Copyright Statement Copyright 2009 American Physical Society. 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 80
Issue Number 5
Page from 052114-1
Page to 052114-22
ISSN 1050-2947
Date Accessioned 2009-11-25
Date Available 2010-08-27T06:56:27Z
Language en_AU
Research Centre Centre for Quantum Dynamics
Faculty Faculty of Science, Environment, Engineering and Technology
Subject Quantum Information, Computation and Communication; Quantum Optics
URI http://hdl.handle.net/10072/30941
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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