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Journal Articles Science Year : 2013

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 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.

Dates and versions

hal-00845258 , version 1 (16-07-2013)



Michael Hatridge, Shyam Shankar, Mazyar Mirrahimi, F. Schackert, K. Geerlings, et al.. Quantum back-action of an individual variable-strength measurement. Science, 2013, 339, pp.178--181. ⟨10.1126/science.1226897⟩. ⟨hal-00845258⟩


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