Optimal reference states for maximum accessible entanglement under the local-particle-number superselection rule

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Title Optimal reference states for maximum accessible entanglement under the local-particle-number superselection rule
Author White, Graham Albert; Vaccaro, Joan Alfina; Wiseman, Howard Mark
Journal Name Physical Review A (Atomic, Molecular and Optical Physics)
Year Published 2009
Place of publication Ridge, NY
Publisher American Physical Society
Abstract Global conservation laws imply superselection rules (SSRs) which restrict the operations that are possible on any given state. Imposing the additional constraint of local operations and classical communication forbids the transfer of quantum systems between spatially separated sites. In the case of particle conservation this imposes a SSR for local particle number. That is, the coherences between subspaces of fixed particle number at each site are not accessible and any state is therefore equivalent to its projection onto these subspaces. The accessible entanglement under the SSR is less than (or equal to) that available in the absence of the SSR. An ancilla can be used as a reference system to increase the amount of accessible entanglement. We examine the relationship between local-particle-number uncertainty and the accessible entanglement and consider the optimal reference states for recovering entanglement from certain systems. In particular we derive the optimal ancilla state for extracting entanglement for a single-shared particle and make steps toward the optimum for general systems. We also show that a reference for phase angle is fundamentally different to a reference for the SSR associated with particle conservation.
Peer Reviewed Yes
Published Yes
Publisher URI http://pra.aps.org/
Alternative URI http://dx.doi.org/10.1103/PhysRevA.77.032114
Copyright Statement Copyright 2008 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 link for access to the definitive, published version.
Volume 79
Page from 032109-1
Page to 032109-13
ISSN 1050-2947
Date Accessioned 2009-04-16
Language en_AU
Research Centre Centre for Quantum Dynamics
Faculty Faculty of Science, Environment, Engineering and Technology
Subject Quantum Information, Computation and Communication
URI http://hdl.handle.net/10072/25626
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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