Reconsidering rapid qubit purification by feedback

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Title Reconsidering rapid qubit purification by feedback
Author Wiseman, Howard Mark; Ralph, J. F.
Journal Name New Journal of Physics
Year Published 2006
Place of publication UK
Publisher Institute of Physics Publishing
Abstract This paper reconsiders the claimed rapidity of a scheme for the purification of the quantum state of a qubit, proposed recently in Jacobs (2003 Phys. Rev. A 67 030301(R)). The qubit starts in a completely mixed state, and information is obtained by a continuous measurement. Jacobs' rapid purification protocol uses Hamiltonian feedback control to maximize the average purity of the qubit for a given time, with a factor of two increase in the purification rate over the no-feedback protocol. However, by re-examining the latter approach, we show that it minimizes the average time taken for a qubit to reach a given purity. In fact, the average time taken for the no-feedback protocol beats that for Jacobs' protocol by a factor of two. We discuss how this is compatible with Jacobs' result and the usefulness of the different approaches.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.iop.org/
Alternative URI http://dx.doi.org/10.1088/1367-2630/8/6/090
Copyright Statement Copyright 2006 Institute of Physics. Reproduced in accordance with the copyright policy of the publisher. This journal is available online please use hypertext links.
Volume 8
Issue Number 6
Page from 1
Page to 11
ISSN 1367-2630
Date Accessioned 2007-03-09
Date Available 2009-10-08T06:28:06Z
Language en_AU
Comments Page numbers are not for citation purposes. Instead, this article has the unique article number of 90.
Research Centre Centre for Quantum Dynamics
Faculty Faculty of Science, Environment, Engineering and Technology
Subject PRE2009-Theoretical Physics
URI http://hdl.handle.net/10072/12363
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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