Scaling quantum systems with silicon carbide and molecules*

Scaling spin-based quantum technologies requires new platforms for creating and controlling quantum states. We begin with the divacancy defect (VV⁰) in silicon carbide (SiC), which combines long lived spin states with a tunable optical interface. First, we leverage the semiconducting host material by integrating single spin qubits into wafer-scale, commercial optoelectronic devices, enabling near terahertz-scale tuning and a mitigation of spectral diffusion in the defect’s optical structure [1].

We then discuss various strategies to extend the coherence of these spin qubits including isotopic purification, clock transitions, pulsed dynamical decoupling, and continuous driving to engineer a decoherence protected subspace [2,3]. These subspaces are decoupled from the major sources of noise, resulting in an over 10,000 times improvement in coherence [3]. Finally, we demonstrate the control and entanglement of a single nuclear spin with an electron spin in SiC. These nuclear memories can further extend coherence and enable multi-qubit quantum registers [2].

Optically addressable spin qubits can also be created, engineered, and scaled through a purely synthetic chemical approach. Moreover, these structures offer new opportunities to construct hybrid systems. We demonstrate the optical initialization and readout, and coherent control, of ground-state spins in organometallic molecules [4]. This bottom-up approach offers avenues to create designer qubits and to deploy the diverse capabilities of chemical synthesis for scalable quantum systems.

References:
[1] C. P. Anderson* and A. Bourassa* et al., Science 366, 6470, 1225-1230 (2019)
[2] A. Bourassa* and C. P. Anderson* et al., Nat. Mat. (2020), arXiv:2005.07602
[3] K. Miao et al., Science 369, 1493–1497 (2020)
[4] S. L. Bayliss*, D. W. Laorenza*, et al., arXiv:2004.07998 (2020)

In collaboration with: C. Anderson, A. Bourassa, K. Miao, S. Bayliss, D. Laorenza, G. Galli, D. Freedman