High-fidelity pulsed qubit readout with a latched cavity state in a parametric circuit-QED system

ORAL

Abstract

Fast and high-fidelity qubit readout remains a key functionality for all quantum processors. Conventional dispersive readout using linear resonators remains inherently limited by signal loss before amplification and the need for fewer readout photons. Here we address these challenges by introducing a parametric circuit-QED architecture comprising a transmon qubit coupled to two weakly nonlinear cavities through a common DC-SQUID coupler. In this configuration, one cavity (the memory mode) stores the qubit information, while the other (the buffer mode) mediates decay into the feedline at a tunable rate. Using a time-sequenced protocol, we exploit the device's nonlinear response and two-photon driving to latch the memory mode to one of two stable cavity states depending on the qubit state. During latching, the memory mode interacts with the buffer through a beam-splitter coupling, which mediates the propagation of the signal to the feedline. This alleviates the problem of qubit decay during integration and helps achieve near-unity state discrimination. The protocol ensures only isolated dispersive qubit-memory mode interactions, minimizing qubit dephasing and Purcell decay. This readout platform is flexible and fully reconfigurable, supporting additional functionalities, such as on-demand reset of the qubit and memory mode, and low-noise amplification of the buffer mode.

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Presenters

  • Sudhir Sahu

    • University of Colorado Boulder, National Institute of Standards and Technology, Department of Physics and Applied Physics, University of Massachusetts Lowell
    • University of Colorado Boulder, National Institute of Standards and Technology
    • National Institute of Standards and Technology

Authors

  • Sudhir Sahu

    • University of Colorado Boulder, National Institute of Standards and Technology, Department of Physics and Applied Physics, University of Massachusetts Lowell
    • University of Colorado Boulder, National Institute of Standards and Technology
    • National Institute of Standards and Technology

  • Zachary Parrott

    • University of Colorado Boulder, National Institute of Standards and Technology
    • National Institute of Standards and Technology, Boulder, Colorado 80305, USA
    • University of Colorado, Boulder
    • University of Colorado Boulder
    • University of Colorado Boulder, National Institute of Standards and Technology Boulder
    • NIST, Boulder

  • Trevyn F.Q. F Larson

    • National Institute of Standards and Technology Boulder
    • National Institute of Standards and Technology
    • University of Colorado
    • University of Colorado Boulder, National Institute of Standards and Technology
    • University of Colorado Boulder, National Institute of Standards and Technology Boulder

  • Debsuvra Mukhopadhyay

    • Northwestern University Evanston

  • Benton T Miller

    • University of Colorado Boulder, National Institute of Standards and Technology
    • University of Colorado, Boulder

  • Tony McFadden

    • National Institute of Standards and Technology Boulder
    • National Institute of Standards and Technology
    • National Institute of Standards and Technology, Boulder CO 80305
    • National Institute of Standards and Technology, Boulder, Colorado 80305, USA
    • National Institute of Standards and Technology (NIST)
    • University of California, Santa Barbara
    • National Institute of Standards and Technology, Boulder

  • Kaixuan Ji

    • University of Colorado Boulder, National Institute of Standards and Technology
    • University of Colorado Boulder, National Institute of Standards and Technology Boulder

  • Tongyu Zhao

    • University of Colorado Boulder, National Institute of Standards and Technology

  • Kristen L Genter

    • University of Colorado Boulder, National Institute of Standards and Technology
    • University of Colorado, Boulder
    • University of Colorado Boulder, National Institute of Standards and Technology Boulder

  • Katarina Cicak

    • National Institute of Standards and Technology Boulder
    • National Institute of Standards and Technology
    • National Institute of Standards and Technology (NIST)

  • Tarush Tiwari

    • University of Massachusetts Lowell

  • Florent Lecocq

    • National Institute of Standards and Technology, University of Colorado Boulder
    • National Institute of Standards and Technology
    • National Institute of Standards and Technology Boulder
    • National Institute of Standards and Technology, Boulder, Colorado 80305, USA
    • National Institute of Standards and Technology Boulder, University of Colorado Boulder

  • Leonardo M Ranzani

    • Raytheon BBN Technologies
    • RTX BBN Technologies, Quantum Photonics and Computing Group, Cambridge, MA
    • RTX BBN Technologies

  • Archana Kamal

    • Northwestern University
    • Northwestern University Evanston, University of Massachusetts Lowell
    • Northwestern University, Evanston, USA
    • University of Massachusetts

  • Ray W Simmonds

    • National Institute of Standards and Technology, University of Colorado Boulder
    • National Institute of Standards and Technology
    • National Institute of Standards and Technology Boulder
    • The Global Coherence Project