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.

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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