Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 5: Transport: Quantum Coherence and Quantum Information Systems 1 (jointly with MA and HL)

TT 5.12: Talk

Monday, March 26, 2012, 12:30–12:45, BH 243

Time-resolved qubit readout via nonlinear Josephson inductance — •Georg Michael Reuther¹, Peter Hänggi¹, and Sigmund Kohler² — ¹Institut für Physik, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany — ²Instituto de Ciencia de Materiales de Madrid (CSIC) C/Sor Juana Inés de la Cruz 3, Cantoblanco 28049 Madrid, Spain

We propose a generalization of dispersive qubit readout which provides the time evolution of a flux qubit observable. Our proposal relies on the non-linear coupling of the qubit to a harmonic oscillator with high frequency, representing a dc-SQUID. Information about the qubit dynamics is obtained by recording the oscillator response to resonant driving and subsequent lock-in detection. We simulate this measurement process for the example of coherent qubit oscillations and, in doing so, we corroborate the underlying measurement relation. In addition, we derive a quantum master equation for the qubit alone. With this at hand, we investigate the dependence of qubit dephasing on the measurement backaction that is induced by the oscillator driving [1].
Georg M. Reuther, David Zueco, Peter Hänggi, and Sigmund Kohler, New J. Phys. 13, 093022 (2011)