Emerging Quantum Spintronics with Semiconductors

Spin-based defects within semiconductors are used to construct devices that enable information processing and sensing technologies based on the quantum nature of electrons and atomic nuclei [1]. These systems have attracted interest as they possess an electronic spin state that can be employed as a quantum bit over a range of temperatures and may be integrated into electronically-active devices. These spin qubit systems have a built-in optical interface that emit in the visible and telecom bands, retain their quantum properties over millisecond timescales or longer, and can be manipulated using a simple combination of light and microwaves. We discuss recent advances in this area including the integration of single spin qubits into silicon carbide (SiC) devices, and significant extension of spin coherence times [2] for scalable technologies.<br/><br/>SiC offers a mature technological platform, clear pathways to device integration, and broad compatibility with CMOS fabrication techniques to address challenges in integration. The neutral divacancy complex (VV0) has been isolated in SiC optoelectronic devices, which results in lifetime limited single-photon emission [3], and present generalized strategies for addressing charge noise sensitivity. We can further improve the fundamental quantum properties of these defects through isotopic engineering of the local nuclear spin environment [4]. Combining all these elements would make divacancy defects in SiC an ideal device integrated platform, with access to both excellent optical properties and long-lived nuclear spin memories.<br/><br/>In addition to exploring the physics of the neutral divacancy (VV0), we are engineering new defect-based spin qubits in SiC. Transition metal ions such as vanadium have host-agnostic orbital structures and operate in the (near) telecom regime [5], and therefore could be naturally integrated into pre-existing telecommunications networks without the need for complicated frequency conversion schemes. With decreasing temperature, we observe a remarkable four-orders-of-magnitude increase in spin relaxation and identify the underlying relaxation mechanisms which involve a two-phonon Orbach process[6]. These results position vanadium as a prime candidate for scalable quantum nodes in future quantum networks.<br/><br/>Finally, we will discuss techniques for the removal and transfer of SiC layers in the tens-of-microns thickness range for heterogenous integration of hybrid quantum systems [7]. By employing new approaches for stressor layer design and crack initiation, we demonstrate controlled spalling of 4H-SiC, the highest fracture toughness material spalled to date. We achieve coherent spin control of neutral divacancy (VV0) qubit ensembles and measure robust spin coherence in the spalled films.<br/> <br/>[1] C. P. Anderson, D. D. Awschalom, Physics Today 76, 26 (2023).<br/>[2] C.P. Anderson et al., Sci. Adv. 8, 5 (2022).<br/>[3] C. P. Anderson, et al. Science, 366, 1225 (2019).<br/>[4] A. Bourassa, et al. Nat. Mater. 19, 1319 (2020).<br/>[5] G. Wolfowicz et al., Sci. Adv. 6, 18 (2020).<br/>[6] J. Ahn et al., arXiv: 2405.16303<br/>[7] C.P. Horn et al., arXiv: 2404.19716