Quantum Back-Action of an Individual Variable-Strength Measurement

• Autores: M. Hatridge, S. Shankar, M. Mirrahimi, F. Schackert, K. Geerlings
• Localización: Science, ISSN 0036-8075, Vol. 339, Nº 6116, 2013, págs. 178-181
• Idioma: inglés
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• Resumen

  • 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.