title: High-fidelity readout in circuit quantum electrodynamics using the Jaynes-Cummings nonlinearity.
abstract: We demonstrate a qubit readout scheme that exploits the Jaynes-Cummings nonlinearity of a superconducting cavity coupled to transmon qubits. We find that, in the strongly driven dispersive regime of this system, there is the unexpected onset of a high-transmission "bright" state at a critical power which depends sensitively on the initial qubit state. A simple and robust measurement protocol exploiting this effect achieves a single-shot fidelity of 87% using a conventional sample design and experimental setup, and at least 61% fidelity to joint correlations of three qubits.
authors.affiliation: Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Reed
authors.forename: L
authors.initials: L
authors.lastname: DiCarlo
authors.forename: B R
authors.initials: BR
authors.lastname: Johnson
authors.forename: L
authors.initials: L
authors.lastname: Sun
authors.forename: D I
authors.initials: DI
authors.lastname: Schuster
authors.forename: L
authors.initials: L
authors.lastname: Frunzio
authors.forename: R J
authors.initials: RJ
authors.lastname: Schoelkopf