High-fidelity gates in a multi-qubit diamond quantum processor (Part I, Gate design)

Spins associated to solid-state color centers might enable a range of quantum technologies. Recent progress using the nitrogen-vacancy center in diamond include the fault-tolerant operation of a logical qubit and the creation of entanglement on a metropolitan scale. It remains a key challenge to obtain high-fidelity gates on the defect center’s electron spin and multiple surrounding nuclear spins [1].



Here, we discuss the challenges in the design of multi-qubit quantum gates on the defect center’s electron and nuclear spins. The always-on couplings between the spins in the system requires gates to be selective, efficient, and robust against decoherence. We investigate different methods of improving our gate design, which combines decoupling of the electron spin with RF driving of the nuclear spins [2], and employ Gate Set Tomography to guide the gate-design process and confirm our findings. Our results provide a path towards reliable multi-qubit quantum processors based on color centers in diamond and other materials.



[1] Bartling et al. Universal high-fidelity quantum gates for spin-qubits in diamond. arXiv:2403.10633 (2024)

[2] Van Ommen et al. Improved Electron-Nuclear Quantum Gates for Spin Sensing and Control. arXiv:2409.13610 (2024)