Dispersive readout of a superconducting flux qubit

Adrian Lupascu

Kavli Institute of Nanoscience Delft, Quantum Transport Group, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands

We present experiments on a superconducting flux qubit measured with a dispersive method. Readout is realized by probing the microwave transmission through a resonator that contains a DC-SQUID coupled to the qubit. For strong driving the resonator has nonlinear response. In both, linear and nonlinear, regimes of resonator driving we observe Rabi oscillations. In the nonlinear regime the resonator is bistable, which results in an increased measurement contrast, as high as 87 %.

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