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dc.contributor.authorLaverick, Kiarn T
dc.contributor.authorChantasri, Areeya
dc.contributor.authorWiseman, Howard M
dc.date.accessioned2021-03-16T04:42:47Z
dc.date.available2021-03-16T04:42:47Z
dc.date.issued2021
dc.identifier.issn2469-9926
dc.identifier.doi10.1103/PhysRevA.103.012213
dc.identifier.urihttp://hdl.handle.net/10072/403184
dc.description.abstractQuantum state smoothing is a technique to construct an estimate of the quantum state at a particular time, conditioned on a measurement record from both before and after that time. The technique assumes that an observer, Alice, monitors part of the environment of a quantum system and that the remaining part of the environment, unobserved by Alice, is measured by a secondary observer, Bob, who may have a choice in how he monitors it. The effect of Bob's measurement choice on the effectiveness of Alice's smoothing has been studied in a number of recent papers. Here we expand upon the Letter which introduced linear Gaussian quantum (LGQ) state smoothing [Phys. Rev. Lett. 122, 190402 (2019)]. In the current paper we provide a more detailed derivation of the LGQ smoothing equations and address an open question about Bob's optimal measurement strategy. Specifically, we develop a simple hypothesis that allows one to approximate the optimal measurement choice for Bob given Alice's measurement choice. By “optimal choice” we mean the choice for Bob that will maximize the purity improvement of Alice's smoothed state compared to her filtered state (an estimated state based only on Alice's past measurement record). The hypothesis, that Bob should choose his measurement so that he observes the back-action on the system from Alice's measurement, seems contrary to one's intuition about quantum state smoothing. Nevertheless, we show that it works even beyond a linear Gaussian setting.
dc.description.peerreviewedYes
dc.languageEnglish
dc.publisherAmerican Psychological Association
dc.relation.ispartofpagefrom012213
dc.relation.ispartofissue1
dc.relation.ispartofjournalPhysical Review A
dc.relation.ispartofvolume103
dc.subject.fieldofresearchPhysical sciences
dc.subject.fieldofresearchcode51
dc.subject.keywordsScience & Technology
dc.subject.keywordsOptics
dc.subject.keywordsPhysics, Atomic, Molecular & Chemical
dc.titleLinear Gaussian quantum state smoothing: Understanding the optimal unravelings for Alice to estimate Bob's state
dc.typeJournal article
dc.type.descriptionC1 - Articles
dcterms.bibliographicCitationLaverick, KT; Chantasri, A; Wiseman, HM, Linear Gaussian quantum state smoothing: Understanding the optimal unravelings for Alice to estimate Bob's state, Physical Review A, 2021, 103 (1), pp. 012213
dc.date.updated2021-03-15T23:26:50Z
dc.description.versionAccepted Manuscript (AM)
gro.rights.copyright© 2021 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.
gro.hasfulltextFull Text
gro.griffith.authorWiseman, Howard M.


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