title: High-contrast dispersive readout of a superconducting flux qubit using a nonlinear resonator.
abstract: 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% of the loss of contrast is unaccounted for. Experiments involving two consecutive detection pulses are consistent with preparation of the qubit state by the first measurement.
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600GA Delft, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Lupaşcu
authors.forename: E F C
authors.initials: EF
authors.lastname: Driessen
authors.forename: L
authors.initials: L
authors.lastname: Roschier
authors.forename: C J P M
authors.initials: CJ
authors.lastname: Harmans
authors.forename: J E
authors.initials: JE
authors.lastname: Mooij