Polytype control of spin qubits in silicon carbide

Abstract

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen-vacancy centres in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials-driven approach that could ultimately lead to ‘designer’ spins with tailored properties. Here we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including states in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron–electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent states, these interactions provide a route to dipole-coupled networks of separately addressable spins.

Spatial mapping of multimode Brownian motions in high-frequency silicon carbide microdisk resonators

“…This could be extended to resolving other ARTICLE mesoscopic non-idealities and defects embedded in the devices. Particularly in SiC, defect spin qubits have already emerged as a promising approach towards room-temperature quantum information processing 47 , with unique polytype control capabilities 48 . The spatially mapped SiC multimode resonances down to the Brownian motion limit makes it possible for new exciting experiments on exploring dynamics and propagation of randomly or rationally patterned defects arrays, and coupling defect spin qubits with multiple radio-frequency high-Q mechanical modes.…”

Polarizing Nuclear Spins in Silicon Carbide

“…Much like the diamond nitrogen-vacancy center [24,25], these color centers have electronic spin states that can be addressed at either ensemble or single-spin levels [18,19] through optically detected magnetic resonance (ODMR). Moreover, spin coherence times can exceed 1 ms [18], and ODMR can persist up to room temperature [10,11,14,19]. Although the fluctuating nuclear spin bath is a principal source of electronic spin decoherence in these types of systems [26], nuclear spins in SiC are not purely detrimental.…”

“…In this dynamic nuclear polarization (DNP) [27,28] process, the optically pumped polarization of electron spins bound to either neutral divacancy [4,5,8,10,14] or PL6 [10,14,16] color centers is transferred to proximate nuclei via the hyperfine interaction. Optically polarizing nuclei in SiC is experimentally straightforward, requiring only broadband illumination and a small external magnetic field (300-500 G), with which we tune color-center ensembles to their ground-state (GS) or excited-state (ES) spin-level anticrossings (the GSLAC and ESLAC, respectively).…”

“…Among its several inequivalent forms, those aligned to the crystal's c axis have the same C 3v symmetry as the nitrogen-vacancy center in diamond. They are the hh and kk divacancies in 4H-SiC [4,5], and the hh, k 1 k 1 , and k 2 k 2 divacancies in 6H-SiC [14,42,43], where the h (hexagonal site) and k (quasicubic site) labels represent the inequivalent lattice sites for vacancies in the SiC lattice. The physical structure of the c-axis-oriented PL6 defect in 4H-SiC [10,14,16] is currently undetermined, but a close relationship to the neutral divacancies is indicated by its similar optical and spin resonances [10], radiative lifetimes [16], and hyperfine spectrum (measured here, see Table I).…”

“…Optical illumination polarizes the color centers' electronic spins into the m S ¼ 0 sublevel [44], a consequence of a spin-dependent intersystem crossing [8,14,18,21]. The degree of optically pumped electronic polarization for divacancies in SiC is at least 60% [14].…”