Abstract
We present a quantitative theory of the suppression of the optical linewidth due to charge fluctuation noise in a - diode, recently observed by Anderson et al. [Science 366, 1225 (2019)]. We connect the local electric field with the voltage across the diode, allowing the identification of the defect depth from the experimental threshold voltage. Furthermore, we show that an accurate description of the decoherence of such spin centers requires a complete spin-1 formalism that yields a biexponential decoherence process, and predict how reduced charge fluctuation noise suppresses the spin center’s decoherence rate.
3 More- Received 27 September 2020
- Revised 22 June 2021
- Accepted 15 July 2021
DOI:https://doi.org/10.1103/PRXQuantum.2.040310
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
An extensive search continues for materials and structures that resist fluctuations of their environment; such “coherent” properties are useful for quantum computation, for sensitive probes of electric, magnetic, or gravitational fields, and to network multiple quantum systems. For coherent spins associated with atomic-scale defects in solids, scalable control requires shifting the energies of the optical transitions used to initialize or read out the coherent quantum state of the defect, and removal of environmental contributions to optical linewidths is required to generate indistinguishable photons. Remarkable shifts and narrowing of the optical transition linewidths were recently achieved experimentally by embedding coherent divacancy spins in a silicon carbide electrical device; however, these demonstrations did not address the fundamental limits of this control or provide a predictive theory.
Here the theoretical foundation for understanding quantum coherence in solid-state qubits is provided. The shifts in optical transition energies and the reduction in optical linewidths are directly connected to fundamental properties of the electrical device, which reveals the importance of both charge fluctuations near the spin center and charge fluctuations in the device contacts. Far greater optical transition energy shifts are possible with different diode designs, and for similar systems increases in the spin coherence times are also predicted. The results identify a novel spin coherence regime fundamental to spin-1 defects in lattices with threefold symmetry and provide direct predictions of the effects of the fluctuating charges on this coherence. The clear set of predictive equations, calculations, and other results provided here will help the design of semiconductor electronic devices for fine control of the properties of quantum spin centers.