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Repetitive Quantum Nondemolition Measurement of a Silicon Spin Qubit Using Different Decodings

ORAL

Abstract

Silicon spin qubits show great promise for fault-tolerant quantum computing. As an essential step towards practical quantum error correction, quantum nondemolition (QND) measurements are needed to efficiently detect the state of a logical qubit without totally losing track of its state. Here we implement QND measurements in a Si/SiGe two-qubit system [1], with one qubit as the logical qubit and the other as the ancilla. Making use of a two-qubit controlled-rotation gate, the state of the logical qubit is mapped onto the ancilla, followed by a destructive readout of the ancilla. In contrast, QND measurement does not destroy the logical qubit but keeps it at the same state after the collapse caused by the first measurement, which allows us to enhance the readout fidelity by multiple QND measurements. Moreover, we also make use of a new analysis method called soft decoding to extract additional information on the state of the logical qubit [2]. We compare the two methods and discuss the conditions for which soft decoding provides an advantage.
[1] T. F. Watson, et al., Nature (2018).
[2] B. D’Anjou and W. A. Coish, PRL (2014).

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Presenters

  • Xiao Xue

    Delft University of Technology

Authors

  • Xiao Xue

    Delft University of Technology

  • Benjamin D'Anjou

    McGill University and University of Konstanz

  • Thomas F Watson

    Delft University of Technology

  • Dan R. Ward

    Sandia National Laboratories, University of Wisconsin-Madison

  • Donald E Savage

    University of Wisconsin-Madison

  • Max G Lagally

    Materials Science and Engineering, University of Wisconsin - Madison, Madison, WI USA, University of Wisconsin-Madison

  • Mark G Friesen

    University of Wisconsin - Madison, Department of Physics, University of Wisconsin-Madison, Madison WI, USA, University of Wisconsin-Madison

  • Susan Nan Coppersmith

    University of Wisconsin - Madison, University of New South Wales, Sydney, Australia, Department of Physics, University of Wisconsin-Madison, University of Wisconsin-Madison, University of New South Wales, University of Wisconsin-Madison, The University of New South Wales

  • Mark Alan Eriksson

    University of Wisconsin - Madison, Physics, University of Wisconsin - Madison, Madison, WI USA, Department of Physics, University of Wisconsin-Madison, Madison WI, USA, Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA, University of Wisconsin-Madison

  • William Coish

    Physics, McGill University, Montreal, Canada, McGill Univ, McGill University, Department of Physics, McGill University

  • Lieven M Vandersypen

    QuTech and Kavli Institute of Nanoscience, TU Delft, The Netherlands, QuTech and Kavli Institute of Nanoscience, QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft University of Technology, Delft University of Technology, Delft, The Netherlands