title: Coherent state evolution in a superconducting qubit from partial-collapse measurement.
abstract: Measurement is one of the fundamental building blocks of quantum-information processing systems. Partial measurement, where full wavefunction collapse is not the only outcome, provides a detailed test of the measurement process. We introduce quantum-state tomography in a superconducting qubit that exhibits high-fidelity single-shot measurement. For the two probabilistic outcomes of partial measurement, we find either a full collapse or a coherent yet nonunitary evolution of the state. This latter behavior explicitly confirms modern quantum-measurement theory and may prove important for error-correction algorithms in quantum computation.
authors.affiliation: Department of Physics and California NanoSystems Institute, University of California, Santa Barbara, CA 93106, USA.
authors.forename: N
authors.initials: N
authors.lastname: Katz
authors.forename: M
authors.initials: M
authors.lastname: Ansmann
authors.forename: Radoslaw C
authors.initials: RC
authors.lastname: Bialczak
authors.forename: Erik
authors.initials: E
authors.lastname: Lucero
authors.forename: R
authors.initials: R
authors.lastname: McDermott
authors.forename: Matthew
authors.initials: M
authors.lastname: Neeley
authors.forename: Matthias
authors.initials: M
authors.lastname: Steffen
authors.forename: E M
authors.initials: EM
authors.lastname: Weig
authors.forename: A N
authors.initials: AN
authors.lastname: Cleland
authors.forename: John M
authors.initials: JM
authors.lastname: Martinis
authors.forename: A N
authors.initials: AN
authors.lastname: Korotkov