Quantum Back-Action of an Individual Variable-Strength Measurement

Measuring a quantum system can randomly perturb its state. The strength and nature of this back-action depend on the quantity that is measured. In a partial measurement performed by an ideal apparatus, quantum physics predicts that the system remains in a pure state whose evolution can be tracked pe...

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Bibliographic Details
Published inScience (American Association for the Advancement of Science) Vol. 339; no. 6116; pp. 178 - 181
Main Authors Hatridge, M., Shankar, S., Mirrahimi, M., Schackert, F., Geerlings, K., Brecht, T., Sliwa, K. M., Abdo, B., Frunzio, L., Girvin, S. M., Schoelkopf, R. J., Devoret, M. H.
Format Journal Article
LanguageEnglish
Published Washington, DC American Association for the Advancement of Science 11.01.2013
The American Association for the Advancement of Science
American Association for the Advancement of Science (AAAS)
Subjects
Amplifiers
Classical and quantum physics: mechanics and fields
Condensed Matter
Control systems
Exact sciences and technology
Feedback
Feedback control
Foundations, theory of measurement, miscellaneous theories (including aharonov-bohm effect, bell inequalities, berry's phase)
Geometric lines
Histograms
Holes
Microwave resonance
Microwaves
Other
Photons
Physics
Quantum information
Quantum mechanics
Quantum Physics
Quantum theory
Qubits (quantum computing)
Signals
Standard deviation
Superconductivity
Tomography
Tracking
Quantum system
Quantum information
Quantum measurement
Quantum bit
Pulse sequence
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Summary:Measuring a quantum system can randomly perturb its state. The strength and nature of this back-action depend on the quantity that is measured. In a partial measurement performed by an ideal apparatus, quantum physics predicts that the system remains in a pure state whose evolution can be tracked perfectly from the measurement record. We demonstrated this property using a superconducting qubit dispersively coupled to a cavity traversed by a microwave signal. The back-action on the qubit state of a single measurement of both signal quadratures was observed and shown to produce a stochastic operation whose action is determined by the measurement result. This accurate monitoring of a qubit state is an essential prerequisite for measurement-based feedback control of quantum systems.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0036-8075
1095-9203
DOI:10.1126/science.1226897