AVS 65th International Symposium & Exhibition
    Materials and Processes for Quantum Computing Focus Topic Monday Sessions
       Session MP+EM+MN+NS-MoM

Paper MP+EM+MN+NS-MoM5
Active Protection of a Superconducting Qubit against Josephson Amplifier Backaction

Monday, October 22, 2018, 9:40 am, Room 203A

Session: Systems and Devices for Quantum Computing I
Presenter: Baleegh Abdo, IBM T. J. Watson Research Center
Authors: B. Abdo, IBM T. J. Watson Research Center
N.T. Bronn, IBM T. J. Watson Research Center
O. Jinka, IBM T. J. Watson Research Center
S.B. Olivadese, IBM T. J. Watson Research Center
A. Corcoles, IBM T. J. Watson Research Center
M. Brink, IBM T. J. Watson Research Center
R. Lake, National Institute of Standards and Technology
D.P. Pappas, National Institute of Standards and Technology
J.M. Chow, IBM T. J. Watson Research Center
Correspondent: Click to Email
Nonreciprocal microwave devices, e.g., isolators and circulators, are key components in high-fidelity, quantum-nondemolition (QND), measurement schemes. They separate input from output and protect the quantum systems from unwanted backaction originated by the output chain. However, state-of-the-art, cryogenic circulators and isolators are disadvantageous in scalable architectures because they are lossy, bulky and use magnetic materials and strong magnetic fields, which are not compatible with superconducting circuits. In this work, we realize and characterize nonreciprocal, superconducting devices suitable for qubit readout, which are formed by coupling two nondegenerate Josephson mixers in interferometric schemes. Nonreciprocity is generated by applying a phase gradient between the same-frequency pumps feeding the devices, which play the role of the magnetic field in a Faraday medium. We incorporate these Josephson-based, nonreciprocal devices into a qubit setup and demonstrate fast, high-fidelity, QND measurements of the qubit while actively protecting it against Josephson amplifier backaction.