Resonantly driven iSWAP operations in a two-hole spin qubit system in germanium

In semiconductor spin qubit systems, both the CZ [1,2] and SWAP [3] gates have been explored, with the former achieving fidelities above 99% [1,2]. However, the iSWAP gate has not yet been characterized. We demonstrate an iSWAP gate between two hole spin qubits in a Ge/SiGe double quantum dot. By resonantly modulating the exchange coupling between the spins via a barrier gate, we induce swap oscillations. We establish a set of calibration routines to tune the iSWAP gate parameters for both the adiabatic and diabatic regimes. Using interleaved randomized benchmarking and quantum process tomography, we obtain maximum fidelities of 93.8% and 88.9% for the diabatic and adiabatic cases, respectively. This work benchmarks the resonantly driven iSWAP gate in Ge for the first time.

[1] Xue, X., Russ, M., Samkharadze, N. et al. Quantum logic with spin qubits crossing the surface code threshold. Nature 601, 343–347 (2022).

[2] C.-A. Wang, V. John, H. Tidjan et al. “Operating semiconductor quantum processors with hopping spins”. Science 385, 447–452 (2024).

[3] Sigillito, A.J., Gullans, M.J., Edge, L.F. et al. Coherent transfer of quantum information in a silicon double quantum dot using resonant SWAP gates. npj Quantum Inf 5, 110 (2019).