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

TL;DR

This study demonstrates high-fidelity coherent control and long relaxation times of chromium ions in commercial silicon carbide, highlighting their potential as optically active spin qubits for quantum technologies.

Contribution

It reports the first high-quality implantation and control of Cr4+ ions in commercial SiC, achieving improved optical linewidths and long spin coherence times.

Findings

Optical linewidth improved to 31 MHz after annealing.

Achieved spin readout fidelity of 79%.

T1 times exceed 1 second at 15 K.

Abstract

Transition metal ions provide a rich set of optically active defect spins in wide bandgap semiconductors. Chromium (Cr4+) 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 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 second at cryogenic temperatures (15 K) with a T2* = 317 nanoseconds and a T2 = 81 microseconds, where spin dephasing times are currently limited by spin-spin interactions within the defect ensemble. Our results demonstrate the potential of Cr4+ in SiC as an extrinsic, optically active spin qubit.