Identification and Creation of the Room-Temperature CoherentlyControllable ST1 Spin Center in Diamond

Among hundreds of optically active solid-state defects, very few of them hold the promise of spin qubits coherentlyoperating at room temperature. Besides the prominent nitrogen-vacancy (NV) center in diamond, the more recently discovered ST1center possesses advantageous electronic and spin properties such as a spin-free ground state and a large spin readout contrast(>50%) at 300 K. However, because of its unknown nature, the ST1 center was never created on demand or computed theoretically.Here, we show that both oxygen and the lattice vacancy are constituents of the ST1 center. The involvement of oxygen isunambiguously proved from two independent experiments conducted on two different samples. The creation efficiency of ST1 at1200 degrees C annealing is about 10-5for oxygen implantation of energy 6-50 keV. The addition of vacancies followed by a thermaltreatment activate further oxygen into ST1 centers, as it does for native nitrogen into NV centers. Possible ST1 configurations arediscussed. The ST1 creation competes with the likely more efficient formation of OV and OVH defects. The controlled fabricationof ST1 and NV centers opens up the way to scalable room-temperature hybrid qubit systems and universal nuclear spin gates.