title: Improving quantum gate fidelities by using a qubit to measure microwave pulse distortions.
abstract: We present a new method for determining pulse imperfections and improving the single-gate fidelity in a superconducting qubit. By applying consecutive positive and negative π pulses, we amplify the qubit evolution due to microwave pulse distortions, which causes the qubit state to rotate around an axis perpendicular to the intended rotation axis. Measuring these rotations as a function of pulse period allows us to reconstruct the shape of the microwave pulse arriving at the sample. Using the extracted response to predistort the input signal, we are able to reduce the average error per gate by 37%, which enables us to reach an average single-qubit gate fidelity higher than 0.998.
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Gustavsson
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Zernike Institute for Advanced Materials, University of Groningen, 9747AG Groningen, The Netherlands.
authors.forename: Olger
authors.initials: O
authors.lastname: Zwier
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Jonas
authors.initials: J
authors.lastname: Bylander
authors.affiliation: Department of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Yan
authors.affiliation: The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan.
authors.forename: Fumiki
authors.initials: F
authors.lastname: Yoshihara
authors.affiliation: The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan and Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904, Japan.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Terry P
authors.initials: TP
authors.lastname: Orlando
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Oliver