High-speed calibration and characterization of superconducting quantum processors without qubit reset

TL;DR

This paper presents a method for rapid calibration and characterization of superconducting qubits using restless measurement techniques that do not require qubit reset, correcting distortions to match traditional measurement accuracy.

Contribution

It extends restless measurement methodology to arbitrary pulse sequences, enabling faster qubit characterization without reset, with effective distortion correction for high-speed quantum device calibration.

Findings

Achieved Rabi oscillation measurement at 250 kHz without reset.

Measured single- and two-qubit gate fidelities 8-20 times faster than reset-based methods.

Demonstrated accurate calibration comparable to traditional methods.

Abstract

To Characterize and calibrate quantum processing devices a large amount of measurement data has to be collected. Active qubit reset increases the speed at which data can be gathered but requires additional hardware and/or calibration. The experimental apparatus can, however, be operated at elevated repetition rates without reset. In this case, the outcome of a first measurement serves as the initial state for the next experiment. Rol. $\textit{et al.}$ used this restless operation mode to accelerate the calibration of a single-qubit gate by measuring fixed-length sequences of Clifford gates which compose to $X$ gates [Phys. Rev. Appl. $7$, 041001 (2017)]. However, we find that, when measuring pulse sequences which compose to arbitrary operations, a distortion appears in the measured data. Here, we extend the restless methodology by showing how to efficiently analyze restless measurements and correct distortions to achieve an identical outcome and accuracy as compared to measurements in which the superconducting qubits are reset. This allows us to rapidly characterize and calibrate qubits. We illustrate our data collection and analysis method by measuring a Rabi oscillation at a $250~\rm{kHz}$ repetition rate without any reset, for a qubit with a decay rate of $1/2\pi T_1=3~\rm{kHz}$. We also show that we can measure a single- and a two-qubit average gate fidelity with Randomized Benchmarking 20 and 8 times faster, respectively, than measurements that reset the qubits through $T_1$-decay.