Digital Predistortion for Flux Control of Tunable Superconducting Qubits

TL;DR

This paper introduces a digital predistortion framework that corrects control signal distortions in flux-tunable superconducting qubits, improving gate fidelity and enabling rapid calibration of quantum processors.

Contribution

The authors develop and experimentally validate a DPD method combining IIR and FIR filters to compensate for flux control distortions in superconducting qubits.

Findings

Successful correction of flux control step-response distortions

Compensated signals show sub-percent deviations from ideal behavior

Enables automated rapid calibration of flux control channels

Abstract

Flux-tunable superconducting qubits rely on fast flux control pulses to implement two-qubit entangling quantum gates, a key building block for quantum algorithms. However, distortion effects introduced by non-ideal control electronics, parasitic components, and the cryogenic quantum chip response can all degrade the gate fidelity. We present a digital predistortion (DPD) framework for characterizing and then compensating for these distortions using a combination of infinite impulse response (IIR) and finite impulse response (FIR) filters. Experiments on a flux-tunable quantum processing unit (QPU) demonstrate a successful correction of step-response distortions on the flux-control line, with a compensated control signal showing only sub-percent deviations from the ideal target linear behavior. The demonstrated method enables automated rapid calibration of flux control channels for superconducting QPUs.