Coherent control and high-fidelity readout of chromium ions in commercial silicon carbide

Abstract

Transition metal ions provide a rich set of optically active defect spins in wide bandgap semiconductors. Chromium (Cr 4+ ) in silicon-carbide (SiC) produces a spin-1 ground state with a narrow, spectrally isolated, spin-selective, near-telecom optical interface. However, previous studies were hindered by material quality resulting in limited coherent control. In this work, we implant Cr into commercial 4H-SiC and show optimal defect activation after annealing above 1600 o C. We measure an ensemble optical hole linewidth of 31 MHz, an order of magnitude improvement compared to as-grown samples. An in-depth exploration of optical and spin dynamics reveals efficient spin polarization, coherent control, and readout with high fidelity (79%). We report T1 times greater than 1 s at cryogenic temperatures (15 K) with a T2 * = 317 ns and a T2 = 81 μs, where spin dephasing times are currently limited by spin-spin interactions within the defect ensemble. Our results demonstrate the potential of Cr 4+ in SiC as an extrinsic, optically active spin qubit.

Quantum simulations of materials on near-term quantum computers

“…Upon solving the effective Hamiltonian, we predict the lowest excited state to be a 1 E state arising from e → e spin-flip transition, with excitation energy of 1.09 (0.86) eV based on embedding calculations beyond (within) the RPA. Results including exchange-correlation effects are in better agreement with the measured ZPL of 1.19 eV 37 , where the Stokes energy is expected to be small given the large Debye-Waller factor 39 . There is currently no experimental report for the triplet excitation energies of Cr in 4H-SiC, but our results are in good agreement with existing experimental measurements for Cr in GaN, a host material with a crystal field strength similar to that of 4H-SiC 38 .…”

“…In this work, we present a quantum embedding theory built on DFT, which is scalable to large systems and which includes the effect of exchange-correlation interactions of the environment on active regions, thus going beyond commonly adopted approximations. In order to demonstrate the effectiveness and accuracy of the theory, we compute ground and excited state properties of several spin-defects in solids including the negatively charged nitrogen-vacancy (NV) center [24][25][26][27][28][29][30] , the neutral silicon-vacancy (SiV) center [31][32][33][34][35][36] in diamond, and the Cr impurity (4+) in 4H-SiC [37][38][39] . These spin-defects are promising platforms for solid-state quantum information technologies, and they exhibit stronglycorrelated electronic states that are critical for the initialization and read-out of their spin states [40][41][42][43][44][45] .…”

Spin–spin interactions in defects in solids from mixed all-electron and pseudopotential first-principles calculations

“…In recent years, much effort has been devoted to realizing spin defects in industrially mature host materials with properties similar or superior to those of diamond NV centers. For instance, several promising spin defects have been identified in silicon carbide, including the divacancy (VV) 8,9 , Cr [10][11][12] , and V impurities 13 . There is also a growing interest in discovering and designing spin qubits in piezo-electric materials such as aluminum nitride 14,15 , in oxides 16 , and in 2D materials 17,18 .…”

Fluorescent Silicon Carbide Nanoparticles

“…Several color centers observed in SiC have also been identified and studied as single photon emitters (V Si , [ 165 ] V Si V C , [ 166 ] C Si V C , [ 151 ] V Si N C , [ 167 ] and Vanadium [ 168 ] ), and as spin qubits (V Si , [ 169 ] V Si V C , [ 146 ] Cr, [ 170 ] Vanadium, [ 168 ] and V Si N C [ 171,172 ] ) in bulk SiC.…”