Room temperature coherent control of defect spin qubits in silicon carbide

Abstract

Electronic spins in semiconductors have been used extensively to explore the limits of external control over quantum mechanical phenomena. A long-standing goal of this research has been to identify or develop robust quantum systems that can be easily manipulated, for future use in advanced information and communication technologies. Recently, a point defect in diamond known as the nitrogen-vacancy centre has attracted a great deal of interest because it possesses an atomic-scale electronic spin state that can be used as an individually addressable, solid-state quantum bit (qubit), even at room temperature. These exceptional quantum properties have motivated efforts to identify similar defects in other semiconductors, as they may offer an expanded range of functionality not available to the diamond nitrogen-vacancy centre. Notably, several defects in silicon carbide (SiC) have been suggested as good candidates for exploration, owing to a combination of computational predictions and magnetic resonance data. Here we demonstrate that several defect spin states in the 4H polytype of SiC (4H-SiC) can be optically addressed and coherently controlled in the time domain at temperatures ranging from 20 to 300 kelvin. Using optical and microwave techniques similar to those used with diamond nitrogen-vacancy qubits, we study the spin-1 ground state of each of four inequivalent forms of the neutral carbon-silicon divacancy, as well as a pair of defect spin states of unidentified origin. These defects are optically active near telecommunication wavelengths, and are found in a host material for which there already exist industrial-scale crystal growth and advanced microfabrication techniques. In addition, they possess desirable spin coherence properties that are comparable to those of the diamond nitrogen-vacancy centre. This makes them promising candidates for various photonic, spintronic and quantum information applications that merge quantum degrees of freedom with classical electronic and optical technologies.

Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide

“…Such single quantum systems have been realized using quantum dots 6 , colour centres in diamond 7 , dopants in nanostructures 8 and molecules 9 . More recently, ensemble emitters with spin dephasing times in the order of microseconds and room-temperature optically detectable magnetic resonance (ODMR) have been identified in silicon carbide (SiC) [10][11][12] , a compound being highly compatible to up-to-date semiconductor device technology. Until recently, however, the engineering of such spin centres in SiC on the single-emitter level has remained elusive 13 .…”

“…In particular, the zero-phonon lines (ZPLs) of V Si -related defects in 4H and 6H polytypes of SiC present spectrally narrow features at near-infrared (NIR) wavelengths (l ZPL ¼ 850-1,200 nm) 10,[14][15][16] . Rayleigh scattering losses in photonic structures are inversely proportional to the fourth power of the wavelength 17,18 , giving almost one order of magnitude lower losses for these defects compared with the nitrogen-vacancy defect in diamond (l ZPL ¼ 637 nm) 19 or the carbon antisite-vacancy pair in SiC (l ZPL ¼ 660 nm) 20 .…”

Frontiers in diffraction unlimited optical methods for spin manipulation, magnetic field sensing and imaging using diamond nitrogen vacancy defects

“…Finally NV centres, even if not discussed here, occupies a special place as possible fl ying qubit for remote entangling of spin qubits in solid state, due to its optical-spin polarization properties and its possible integration in quantumhybrid-spin systems (e.g., NV and magnetic single molecules). Other deep centres as NV centre in diamond and in similar wide-bandgap semiconductors, such as SiC are under investigation [18,66] ; we are witnessing either a new era of research of another NV-like centre in solid state or the establishing of novel advanced technologies in the above-mentioned fi elds.…”

Controllable quantum spin glasses with magnetic impurities embedded in quantum solids

“…Furthermore, the range of atoms and molecules that can be matrix isolated is quite broad and is not limited to the species that can be laser cooled 23,24 or associated from ultracold atoms 25,26 . In a way, atoms or molecules trapped in matrices behave similarly to defects in solids 20,21 . However, such impurities can feature substantially higher magnetic or electric dipole moments compared to defect centers, resulting in significantly enhanced interaction strengths.…”

“…Under these conditions, individual atoms possess very long coherence times (T 1 , T 2 ), and can be optically pumped, with high efficiency, into a given internal state or set of internal states 18 . As we show below, a matrix-embedded atom can be regarded as a highly controllable, quantumcoherent degree of freedom featuring strong dipolar interactions, analogous to ultracold atoms in optical lattices 19 and solid-state defect centers 20,21 .…”