Resonant two-qubit gates for fermionic simulations with spin qubits

TL;DR

This paper introduces a novel method to implement a versatile set of fermionic two-qubit gates in spin qubits using a single pulse, improving efficiency and fidelity for quantum simulations.

Contribution

The authors demonstrate a new approach to realize the full fSim gate set in spin qubits with minimal gate duration and drive amplitude, validated by high-fidelity experimental results.

Findings

Achieved a 93.8% fidelity for the resonant iSWAP gate.

Validated the method with quantum process tomography.

Identified qubit decoherence as the main error source.

Abstract

In gate-defined semiconductor spin qubits, the highly tunable Heisenberg exchange interaction is leveraged to implement fermionic two-qubit gates such as CZ and SWAP. However, the broader family of fermionic simulation (fSim) gates remains unexplored, and has the potential to enhance the performance of near-term quantum simulation algorithms. Here, we demonstrate a method to implement the fSim gate set in spin qubits using a single pulse combining baseband and resonant exchange drives. This approach minimizes gate duration and drive amplitude, mitigating decoherence and crosstalk. We validate its effectiveness by realizing a resonant iSWAP gate between two hole spins in germanium, achieving a fidelity of 93.8(5)% extracted with interleaved randomized benchmarking. Quantum process tomography confirms accurate gate calibration and identifies qubit decoherence as the dominant error source. Our results establish a practical route toward a versatile and efficient two-qubit gate set for spin-based quantum processors.