Real-time two-axis control of a spin qubit

Nature Communications, vol. 15, pp. 1676

Abstract

Optimal control of qubits requires the ability to adapt continuously to their ever-changing environment. We demonstrate a real-time control protocol for a two-electron singlet-triplet qubit with two fluctuating Hamiltonian parameters. Our approach leverages single-shot readout classification and dynamic waveform generation, allowing full Hamiltonian estimation to dynamically stabilize and optimize the qubit performance. Powered by a field-programmable gate array (FPGA), the quantum control electronics estimates the Overhauser field gradient between the two electrons in real time, enabling controlled Overhauser-driven spin rotations and thus bypassing the need for micromagnets or nuclear polarization protocols. It also estimates the exchange interaction between the two electrons and adjusts their detuning, resulting in extended coherence of Hadamard rotations when correcting for fluctuations of both qubit axes. Our study highlights the role of feedback in enhancing the performance and stability of quantum devices affected by quasistatic noise.

Authors 12

1. Fabrizio Berritta corresponding

   University of Copenhagen

   Affiliation as printed

   Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark. fabrizio.berritta@nbi.ku.dk

   Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark

2. Torbjørn Rasmussen

   University of Copenhagen

   Affiliation as printed

   Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark

3. Jan A. Krzywda Aachen Lorentz Institute and Leiden Institute of Advanced Computer Science

   Leiden University

   Affiliation as printed

   Lorentz Institute and Leiden Institute of Advanced Computer Science, Leiden University, P.O. Box 9506, 2300 RA, Leiden, The Netherlands

4. Joost van der Heijden
   Affiliation as printed

   QDevil, Quantum Machines, 2750, Ballerup, Denmark

5. Federico Fedele

   University of Copenhagen

   Affiliation as printed

   Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark

6. Saeed Fallahi

   Purdue University West Lafayette

   Affiliation as printed

   Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA

   Department of Physics and Astronomy, Purdue University, West Lafayette, IN, 47907, USA

7. G. C. Gardner

   Purdue University West Lafayette

   Affiliation as printed

   Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA

8. Michael J. Manfra

   Purdue University West Lafayette

   Affiliation as printed

   Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA

   Department of Physics and Astronomy, Purdue University, West Lafayette, IN, 47907, USA

   Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA

   School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA

9. Evert van Nieuwenburg Aachen Lorentz Institute and Leiden Institute of Advanced Computer Science

   Leiden University

   Affiliation as printed

   Lorentz Institute and Leiden Institute of Advanced Computer Science, Leiden University, P.O. Box 9506, 2300 RA, Leiden, The Netherlands

10. Jeroen Danon

    Norwegian University of Science and Technology

    Affiliation as printed

    Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway

11. Anasua Chatterjee corresponding

    University of Copenhagen

    Affiliation as printed

    Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark. anasua.chatterjee@nbi.ku.dk

    Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark

12. Ferdinand Kuemmeth corresponding

    University of Copenhagen

    Affiliation as printed

    Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark. kuemmeth@nbi.dk

    QDevil, Quantum Machines, 2750, Ballerup, Denmark. kuemmeth@nbi.dk

    Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark

    QDevil, Quantum Machines, 2750, Ballerup, Denmark