Towards high-fidelity gates for spin qubits in diamond

Optically active spin qubits in solid-state materials are a promising platform for quantum networks and distributed quantum computation. Recent advances include entanglement over a three-node network and the fault-tolerant operation of a logical quantum bit of an error correction code. A key challenge for larger networks and computations is to further increase the single-qubit and two-qubit gate fidelities. In this work, we use two-qubit gate set tomography (GST) to characterize and optimize gate fidelities for spin qubits in diamond. By comparing the experimental results with numerical simulations, we discuss the current limitations of the gates. These results will help understand and subsequently improve quantum gates for quantum information processes and quantum networks based on the NV center in diamond, as well as other spin qubits in a variety of materials.