High-contrast dispersive readout of a superconducting flux qubit using a nonlinear resonator

Lupascu, A.; Driessen, E. F. C.; Roschier, L.; Harmans, C. J. P. M.; Mooij, J. E.

High-contrast dispersive readout of a superconducting flux qubit using a nonlinear resonator

Authors

Description

We demonstrate high-contrast state detection of a superconducting flux qubit. Detection is realized by probing the microwave transmission of a nonlinear resonator, based on a SQUID. Depending on the driving strength of the resonator, the detector can be operated in the monostable or the bistable mode. The bistable operation combines high-sensitivity with intrinsic latching. The measured contrast of Rabi oscillations is as high as 87 %; of the missing 13 %, only 3 % is unaccounted for. Experiments involving two consecutive detection pulses are consistent with preparation of the qubit state by the first measurement.
submitted to Phys. Rev. Lett