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Weak measurement
In quantum mechanics (and computation & information), weak measurement is a type of quantum measurement that results in an observer obtaining very little information about the system on average, but also disturbs the state very little.[1] From Busch's theorem[2] any quantum system is necessarily disturbed by measurement, but the amount of disturbance is described by a parameter called the measurement strength.
Weak measurement is a subset of the more general form of quantum measurement described by operators known as POVMs, where the strength of measurement is low. In the literature weak measurements are also known as unsharp,[3] fuzzy,[3][4] dull, noisy,[5] approximate, and gentle[6] measurements. Additionally weak measurements are often confused with the distinct but related concept of the weak value.[7]
The most common methods of weak measurement are by coupling the quantum system to an ancilla qubit and projectively measuring the ancilla (which results in a weak measurement on the quantum system of interest), measuring a small part of large entangled systems, and for atomic physics, phase contrast imaging.
- ^ Todd A Brun (2002). "A simple model of quantum trajectories". Am. J. Phys. 70 (7): 719–737. arXiv:quant-ph/0108132. Bibcode:2002AmJPh..70..719B. doi:10.1119/1.1475328. S2CID 40746086.
- ^ Paul Busch (2009). J. Christian; W.Myrvold (eds.). "No Information Without Disturbance": Quantum Limitations of Measurement. Invited contribution, "Quantum Reality, Relativistic Causality, and Closing the Epistemic Circle: An International Conference in Honour of Abner Shimony", Perimeter Institute, Waterloo, Ontario, Canada, July 18–21, 2006. Vol. 73. Springer-Verlag, 2008. pp. 229–256. arXiv:0706.3526. doi:10.1007/978-1-4020-9107-0. ISBN 978-1-4020-9106-3. ISSN 1566-659X.
{{cite book}}:|journal=ignored (help) - ^ a b Gudder, Stan (2005). "Non-disturbance for fuzzy quantum measurements". Fuzzy Sets and Systems. 155 (1): 18–25. doi:10.1016/j.fss.2005.05.009.
- ^ Asher Peres (1993). Quantum Theory, Concepts and Methods. Kluwer. p. 387. ISBN 978-0-7923-2549-9.
- ^ A. N. Korotkov (2003). "Noisy Quantum Measurement of Solid-State Qubits: Bayesian Approach". In Y. v. Nazarov (ed.). Quantum Noise in Mesoscopic Physics. Springer Netherlands. pp. 205–228. arXiv:cond-mat/0209629. doi:10.1007/978-94-010-0089-5_10. ISBN 978-1-4020-1240-2. S2CID 9025386.
- ^ Cite error: The named reference
Winter1999was invoked but never defined (see the help page). - ^ Yakir Aharonov; David Z. Albert & Lev Vaidman (1988). "How the result of a measurement of a component of the spin of a spin-1/2 particle can turn out to be 100". Physical Review Letters. 60 (14): 1351–1354. Bibcode:1988PhRvL..60.1351A. doi:10.1103/PhysRevLett.60.1351. PMID 10038016. S2CID 46042317.
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