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TT: Fachverband Tiefe Temperaturen

TT 9: Transport: Quantum Coherence and Quantum Information Systems

TT 9.5: Talk

Monday, February 25, 2008, 15:15–15:30, H 2053

Theory of quantum non-demolition measurements of a flux qubit — •Luca Chirolli and Guido Burkard — Institute of Theoretical Physics C, RWTH Aachen University, D-52056 Aachen, Germany

Recently a new technique for a quantum non demolition measurement (QND) of the state of a flux qubit based on the coupling to a circuit oscillator has been proposed and experimentally realized (A. Lupascu et al., Nature Physics 3, 119 (2007)). In our theoretical description of the experiment, we use the positive operator value measurement (POVM) formalism to describe the qubit measurement. Two mechanisms lead to deviations from a perfect QND measurement: (i) the quantum fluctuations of the measurement oscillator, and (ii) quantum tunneling between the qubit states |0⟩ and |1⟩ during measurement.