Vanadium spin qubits as telecom quantum emitters in silicon carbide

{\textit{Ab initio} determination of pseudospin for paramagnetic defects in SiC

“…Indeed, all-optical identification and coherent control of ensemble Mo center have been realized [6]. Parallel to our study, vanadium defects have been isolated and coherent control of single spins have been demonstrated with showing all the ingredients required for a highly efficient spin-photon interface [24].…”

“…and hence cannot be coupled to each other and therefore g ⊥ = 0 (cf. [7]; 160-230 MHz for V Si (h) and 100-190 MHz for V Si (k) [24] in 4H SiC. HF will mix the corresponding wavefunctions only in the second order, thus it is expected that the final g ⊥ factor will be at least two orders of magnitude smaller than that of g .…”

Spin-relaxation times exceeding seconds for color centers with strong spin-orbit coupling in SiC

“…1(b)) [13,15], resembling what is observed for the silicon-vacancy in diamond [21]. Concerning its electronic structure, this defect shares several similarities with the V defect in SiC, which has optical transitions fully compatible with telecommunications infrastructure [13,16,18] Each KD is a doublet composed of a time-reversal pair: the doublet splits as an effective spin-1/2 system in the presence of a magnetic field, but its degeneracy is otherwise protected by time-reversal symmetry (see [22] for a more extensive summary). The energy difference between the two spin-orbit split KD's in the ground state, ∆ orb in Fig.…”

“…However, finding suitable emitters that combine long-lived spins, short excited-state lifetimes and optical transitions compatible with telecommunication fiberoptics infrastructure in an industrially established material has remained elusive. Silicon carbide, a wide bandgap semiconductor with mature fabrication technology, hosts a range of defect centers with optical transitions near or at the telecom range [9,10], including several defects containing transition metal (TM) impurities [11][12][13][14][15][16][17]. The electronic and spin properties of these defects derive largely from the character of the d-orbitals of the TM under the action of a crystal field determined by the lattice site [18][19][20].…”

“…As a consequence, one cannot directly drive spin resonances between the two ground state spin sublevels. Mixing of the ground state KD with states lying at higher energies due to the presence of magnetic, hyperfine or electric fields can, however, lift these restrictions as is observed for V defects in SiC [16]. Although this is expected to provide a contribution to spin relaxation mechanisms, it is also a necessary requirement in order to control the ground state electronic spin via microwaves.…”