Real-time two-axis control of a spin qubit

University of Regensburg Publication Server (University of Regensburg)

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
   Affiliation as printed

   Center for Quantum Devices , Niels Bohr Institute ,

2. Torbjørn Rasmussen
   Affiliation as printed

   Center for Quantum Devices , Niels Bohr Institute ,

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
   Affiliation as printed

   Center for Quantum Devices , Niels Bohr Institute ,

6. Saeed Fallahi

   Purdue University West Lafayette

   Affiliation as printed

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

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

7. Geoffrey C. Gardner

   Purdue University West Lafayette

   Affiliation as printed

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

   Center for Quantum Devices , Niels Bohr Institute ,

8. Michael J. Manfra
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 Aachen Lorentz Institute and Leiden

    Norwegian University of Science and Technology · Lorentz Center

    Affiliation as printed

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

    Lorentz Institute and Leiden

11. Anasua Chatterjee
12. Ferdinand Kuemmeth