IQM reports 99.93% CZ-gate fidelity with simultaneous >99.9% single-qubit and readout fidelities on a tunable-coupler transmon device
An arXiv preprint (2508.16437, submitted 2025-08-22) from a team led by Fabian Marxer at IQM Quantum Computers reports, in a single superconducting device of two transmons coupled by a tunable coupler, a 40-hour-averaged CZ two-qubit gate fidelity of 99.93%, simultaneous single-qubit gate fidelities of 99.98%, and readout fidelities above 99.94%. The result demonstrates that careful tuning of the qubit-coupler couplings can hold all three operation fidelities above 99.9% concurrently in one device.
A named, third-party-verifiable two-qubit gate fidelity of 99.93% from a commercial superconducting-qubit vendor is a credible benchmark with industry-wide implications: holding single-qubit, two-qubit and readout fidelities all above 99.9% in one device is a prerequisite for surface-code operation below threshold. Per section 7.3(b) the named-metric result clears the academic filter; per section 8 a credible benchmark with industry-wide implications sits at the score-6 band. The 99.93% CZ figure is incremental over the ~99.9% state of the art rather than a clear record, which holds it below the named-processor-record band.
Demonstrated simultaneous >99.9% fidelities strengthen IQM's competitive position against the larger superconducting incumbents on the fidelity axis that gates error-correction overhead; the open question is whether the figures hold as the device scales beyond an isolated qubit pair to a full processor.