Randomized benchmarking of quantum gates implemented by electron spin resonance

Area of Science:

• Quantum Information Science
• Magnetic Resonance Spectroscopy
• Solid-State Physics

Background:

• Electron spin systems are crucial for advancing quantum control and error correction.
• Pulsed electron spin resonance (ESR) spectroscopy enables precise manipulation and measurement of quantum states.

Purpose of the Study:

• To introduce a novel X-band pulsed ESR spectrometer engineered for high-fidelity coherent control of electron spins.
• To establish a benchmark for quantum gate performance in spin systems.

Main Methods:

• Utilized a loop-gap resonator for sub-millimeter samples, achieving a control bandwidth of approximately 40 MHz.
• Implemented universal quantum control via single-sideband upconversion with an I-Q modulator and a high-speed arbitrary waveform generator (1.2 GS/s).
• Employed a single-qubit randomized benchmarking protocol on gamma-irradiated quartz to quantify Clifford gate errors.

Main Results:

• Achieved a control bandwidth of ~40 MHz for small samples.
• Quantified average Clifford gate errors using randomized benchmarking.
• Identified inhomogeneous dephasing (1/T2*) as the primary source of gate error through spin packet selection.
• Attained a best average fidelity of 99.2% for Clifford gates.

Conclusions:

• The developed spectrometer enables high-fidelity coherent control of electron spins.
• The achieved 99.2% average gate fidelity provides a new benchmark for quantum spin technologies.
• Inhomogeneous dephasing is a key limiting factor for gate performance in this system.