{"title":"A Theory of Quantum Instruments","authors":"S. Gudder","doi":"10.12743/quanta.v12i1.233","DOIUrl":null,"url":null,"abstract":"Until recently, a quantum instrument was defined to be a completely positive operation-valued measure from the set of states on a Hilbert space to itself. In the last few years, this definition has been generalized to such measures between sets of states from different Hilbert spaces called the input and output Hilbert spaces. This article presents a theory of such instruments. Ways that instruments can be combined such as convex combinations, post-processing, sequential products, tensor products and conditioning are studied. We also consider marginal, reduced instruments and how these are used to define coexistence (compatibility) of instruments. Finally, we present a brief introduction to quantum measurement models where the generalization of instruments is essential. Many of the concepts of the theory are illustrated by examples. In particular, we discuss Holevo and Kraus instruments.Quanta 2023; 12: 27–40.","PeriodicalId":37613,"journal":{"name":"Quanta","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2023-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Quanta","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.12743/quanta.v12i1.233","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"Arts and Humanities","Score":null,"Total":0}
引用次数: 1
Abstract
Until recently, a quantum instrument was defined to be a completely positive operation-valued measure from the set of states on a Hilbert space to itself. In the last few years, this definition has been generalized to such measures between sets of states from different Hilbert spaces called the input and output Hilbert spaces. This article presents a theory of such instruments. Ways that instruments can be combined such as convex combinations, post-processing, sequential products, tensor products and conditioning are studied. We also consider marginal, reduced instruments and how these are used to define coexistence (compatibility) of instruments. Finally, we present a brief introduction to quantum measurement models where the generalization of instruments is essential. Many of the concepts of the theory are illustrated by examples. In particular, we discuss Holevo and Kraus instruments.Quanta 2023; 12: 27–40.
QuantaArts and Humanities-History and Philosophy of Science
CiteScore
1.30
自引率
0.00%
发文量
5
审稿时长
12 weeks
期刊介绍:
Quanta is an open access academic journal publishing original research and review articles on foundations of quantum mechanics, mathematical physics and philosophy of science.