Inverted fine structure of a 6H-SiC qubit enabling robust spin-photon interface

Abstract

Controllable solid-state spin qubits are currently becoming useful building blocks for applied quantum technologies. Here, we demonstrate that in a specific type of silicon-vacancy in the 6H-SiC polytype the excited-state fine structure is inverted, compared to 4H-SiC. From the angular polarization dependencies of the emission, we reconstruct the spatial symmetry and determine the optical selection rules depending on the local deformation and spin–orbit interaction. We show that this system is well suited for the implementation of robust spin–photon entanglement schemes. Furthermore, the inverted fine structure leads to unexpected behavior of the spin readout contrast. It vanishes and recovers with lattice cooling due to two competing optical spin pumping mechanisms. Our experimental and theoretical approaches provide a deep insight into the optical and spin properties of atomic-scale qubits in SiC required for quantum communication and distributed quantum information processing.

Silicon Carbide Photonics Bridging Quantum Technology

“…Most studied are the two (three) distinct V Si – centers in 4H-SiC (6H-SiC) . , The optical properties of V Si – centers are most studied in the 4H polytype, exhibiting a zero phonon line (ZPL) emission at 862 nm for the V1 for the hexagonal lattice site center, and 917 nm for the cubic lattice site center, V2. In the 6H-SiC polytype, the V1, V2, and V3 centers show ZPLs at 865, 887, and 906 nm, respectively. , Additionally, V Si – centers have been observed in the 15R polytype. ,, The spin quantum number of all V Si – centers is S = 3/2.…”

“…In the 6H-SiC polytype, the V1, V2, and V3 centers show ZPLs at 865, 887, and 906 nm, respectively. 154,155 Additionally, V Si − centers have been observed in the 15R polytype. 136,151,156 The spin quantum number of all V Si − centers is S = 3/2.…”

Zero-Field ODMR and relaxation of Si-vacancy centers in 6H-SiC

“…We start the characterisation of the sample with the photoluminescence spectra. Depending on the transition dipole, whose orientation varies with the different types of vacancies [24,29], the PL emission shows an orientation dependence. We therefore recorded PL spectra for emission parallel and perpendicular to the c-axis.…”

“…Comparison of the two sets of spectra shows that V 1 and V 3 emit more PL parallel to the c-axis, while V 2 emits more perpendicular to the c-axis [24,25,30].…”

“…In a previous paper, silicon vacancies in 6H-SiC were characterised [24] in terms of their photoluminescence as well as their spin Hamiltonian, using ODMR. Since ODMR correlates optical properties with energy differences between spin states, it provides a useful approach for associating the zero-field splittings with the emission wavelengths.…”