High-Fidelity Electron Spin Gates in a Scalable Diamond Quantum Register

Diamond is a promising platform for quantum information processing as it can host highly coherent qubits that might allow for the construction of large quantum registers. A prerequisite for such devices is a coherent interaction between electron nitrogen vacancy (NV) spins. Entanglement between dipolar-coupled NV spin pairs has been demonstrated, but with a limited entanglement fidelity and its error sources have not been characterized. Here, we design a robust, easy to implement entangling gate between NV spins in diamond and quantify the influence of multiple error sources on the gate performance. Experimentally, we demonstrate a record gate fidelity of F=(96.0 ± 2.5) % under ambient conditions. Our identification of the dominant errors paves the way towards NV-NV gates beyond the error correction threshold.