Radio-frequency reflectometry of a quantum dot using an ultra-low-noise SQUID amplifier

ORAL

Abstract

Fault-tolerant spin-based quantum computers will require fast and accurate qubit readout. This can be achieved using radio-frequency reflectometry given sufficient sensitivity to the change in quantum capacitance associated with the qubit states. Here, we demonstrate a 23-fold improvement in capacitance sensitivity by supplementing a cryogenic semiconductor amplifier with a SQUID preamplifier. The SQUID amplifier operates at a frequency near 200 MHz and achieves a noise temperature below 550 mK when integrated into a reflectometry circuit, which is within a factor 115 of the quantum limit. It enables a record sensitivity to capacitance of 0.07 aFHz-0.5 and a sensitivity to oscillating charge of 5.9 x 10-24CHz-0.5. We use this circuit to measure the stability diagram of a gate-defined quantum dot, and show that the sensitivity should be sufficient for single-shot readout of a singlet-triplet qubit in GaAs without a charge sensor.

*The work was funded by DSTL (contract 1415Nat-PhD 59), EPSRC (EP/J015067/1, EP/N014995/1), the Royal Academy of Engineering, a Marie Curie Fellowship and Templeton World Charity Foundation.

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Presenters

  • Felix Schupp

    • Princeton University
    • Oxford University-USE 4643

Authors

  • Felix Schupp

    • Princeton University
    • Oxford University-USE 4643

  • Natalia Ares

    • Materials, University of Oxford
    • Department of Materials, University of Oxford
    • Oxford University-USE 4643

  • Aquila Mavalankar

    • Adaptix Ltd
    • Oxford University-USE 4643

  • Jonathan Griffiths

    • University of Cambridge
    • Department of Physics, University of Cambridge
    • Physics, Cambridge University

  • Geb Jones

    • Physics, Cambridge University

  • Ian Farrer

    • University of Sheffield
    • Department of Physics, University of Cambridge
    • Electronic and Electrical Engineering, University of Sheffield
    • Electrical Engineering, University of Sheffield
    • Department of Electronic and Electrical Engineering, University of Sheffield
    • Physics, Sheffield University

  • David A Ritchie

    • University of Cambridge
    • Department of Physics, University of Cambridge
    • Semiconductor Physics, University of Cambridge
    • Physics, University of Cambridge
    • Department of Physics, Cavendish Laboratory
    • Physics, Cambridge University

  • Charles G Smith

    • Department of Physics, University of Cambridge
    • University of Cambridge
    • Physics, Cambridge University

  • George Andrew Davidson Briggs

    • Department of Materials, University of Oxford
    • Oxford University-USE 4643
    • Materials, University of Oxford

  • Edward Laird

    • Department of Physics, Lancaster University
    • Physics, Lancaster University