Randomized benchmarking of quantum gates implemented by electron spin resonance

TL;DR

This paper demonstrates high-fidelity control and benchmarking of electron spin qubits using a specialized pulsed ESR spectrometer, achieving a 99.2% average fidelity for quantum gates, advancing quantum control techniques.

Contribution

It introduces a high-bandwidth ESR spectrometer with optimized control methods and benchmarks electron spin gate fidelity, providing a new standard for quantum control in spin systems.

Findings

Achieved 99.2% average fidelity for Clifford gates.

Identified inhomogeneous dephasing as the main source of error.

Implemented phase transient correction and hardware optimization.

Abstract

Spin systems controlled and probed by magnetic resonance have been valuable for testing the ideas of quantum control and quantum error correction. This paper introduces an X-band pulsed electron spin resonance spectrometer designed for high-fidelity coherent control of electron spins, including a loop-gap resonator for sub-millimeter sized samples with a control bandwidth ~ 40 MHz. Universal control is achieved by a single-sideband upconversion technique with an I-Q modulator and a 1.2 GS/s arbitrary waveform generator. A single qubit randomized benchmarking protocol quantifies the average errors of Clifford gates implemented by simple Gaussian pulses, using a sample of gamma-irradiated quartz. Improvements in unitary gate fidelity are achieved through phase transient correction and hardware optimization. A preparation pulse sequence that selects spin packets in a narrowed distribution of static fields confirms that inhomogeneous dephasing (1/T2*) is the dominant source of gate error. The best average fidelity over the Clifford gates obtained here is 99.2%, which serves as a benchmark to compare with other technologies.