title: Measuring and Suppressing Quantum State Leakage in a Superconducting Qubit.
abstract: Leakage errors occur when a quantum system leaves the two-level qubit subspace. Reducing these errors is critically important for quantum error correction to be viable. To quantify leakage errors, we use randomized benchmarking in conjunction with measurement of the leakage population. We characterize single qubit gates in a superconducting qubit, and by refining our use of derivative reduction by adiabatic gate pulse shaping along with detuning of the pulses, we obtain gate errors consistently below 10^{-3} and leakage rates at the 10^{-5} level. With the control optimized, we find that a significant portion of the remaining leakage is due to incoherent heating of the qubit.
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: Zijun
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: Julian
authors.initials: J
authors.lastname: Kelly
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Quintana
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: R
authors.initials: R
authors.lastname: Barends
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: B
authors.initials: B
authors.lastname: Campbell
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: B
authors.initials: B
authors.lastname: Chiaro
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: A
authors.initials: A
authors.lastname: Dunsworth
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Fowler
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: E
authors.initials: E
authors.lastname: Lucero
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: E
authors.initials: E
authors.lastname: Jeffrey
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.|Department of Materials, University of California, Santa Barbara, California 93106, USA.
authors.forename: A
authors.initials: A
authors.lastname: Megrant
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: J
authors.initials: J
authors.lastname: Mutus
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: M
authors.initials: M
authors.lastname: Neeley
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: C
authors.initials: C
authors.lastname: Neill
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: P J J
authors.initials: PJ
authors.lastname: O'Malley
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: P
authors.initials: P
authors.lastname: Roushan
authors.affiliation: Google Inc., Santa Barbara, California 93117, USA.
authors.forename: D
authors.initials: D
authors.lastname: Sank
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: A
authors.initials: A
authors.lastname: Vainsencher
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wenner
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: White
authors.affiliation: Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Korotkov
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.|Google Inc., Santa Barbara, California 93117, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Martinis