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Calibrating magnetic flux control in superconducting circuits by compensating distortions on timescales from nanoseconds up to tens of microseconds

Christoph Hellings1,2,*, Nathan Lacroix1,2,†, Ants Remm1,2,‡, Richard Boell1, Johannes Herrmann1,2, Stefania Lazăr1,2,§, Sebastian Krinner1,2,§, François Swiadek1,2, Christian Kraglund Andersen1,∥ et al.

Christopher Eichler1,2,¶ and Andreas Wallraff1,2,3

  • 1Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
  • 2Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
  • 3ETH Zurich – PSI Quantum Computing Hub, Paul Scherrer Institute, CH-5232 Villigen, Switzerland

  • *Contact author: christoph.hellings@phys.ethz.ch
  • †Present address: Google Quantum AI, Goleta, CA, USA.
  • ‡Present address: Atlantic Quantum, Cambridge, MA, USA.
  • §Present address: Zurich Instruments AG, Zurich, Switzerland.
  • ∥Present address: QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
  • Present address: Department of Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
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Phys. Rev. Research 7, 043142 – Published 7 November, 2025

DOI: https://doi.org/10.1103/1qhb-r4fb

Abstract

Fast tuning of the transition frequency of superconducting qubits using magnetic flux is essential, for example, for realizing high-fidelity two-qubit gates with low leakage or for reducing errors in dispersive qubit readout. To apply accurately shaped flux pulses, signal distortions induced by the flux control lines need to be carefully compensated for. This requires their in situ characterization at the reference plane of the qubit. However, many existing approaches are limited in time resolution or in pulse duration. Here, we overcome these limitations and demonstrate accurate flux control with subpermille residual frequency errors on timescales ranging from nanoseconds to tens of microseconds. We achieve this by combining two complementary methods to characterize and compensate for pulse distortions. We have deployed this approach successfully in a quantum error correction experiment calibrating 24 flux-activated two-qubit gates. Reliable calibration methods, as the ones presented here, are essential in experiments scaling up superconducting quantum processors.

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Phys. Rev. Research 7, 043142– Published 7 November, 2025
  • Received 7 April 2025
  • Accepted 15 August 2025
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