title: Improved superconducting qubit readout by qubit-induced nonlinearities.
abstract: In dispersive readout schemes, qubit-induced nonlinearity typically limits the measurement fidelity by reducing the signal-to-noise ratio (SNR) when the measurement power is increased. Contrary to seeing the nonlinearity as a problem, here we propose to use it to our advantage in a regime where it can increase the SNR. We show analytically that such a regime exists if the qubit has a many-level structure. We also show how this physics can account for the high-fidelity avalanchelike measurement recently reported by Reed et al. [arXiv:1004.4323v1].
authors.affiliation: Département de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada, J1K 2R1.
authors.forename: Maxime
authors.initials: M
authors.lastname: Boissonneault
authors.forename: J M
authors.initials: JM
authors.lastname: Gambetta
authors.forename: Alexandre
authors.initials: A
authors.lastname: Blais