Spin Dynamics of Single Quantum Defects*

Realizing spin qubits for quantum computing and sensing applications relies on the ability to predict the response of a spinful quantum defect to both intentional and unintentioanl external perturbations from first principles. Intentional perturbations include spin interactions with various bosons, including photons, phonons and magnons, whereas unintentional ones include the role of fluctuating charges or spins in the environment. Simulating these perturbations requires a rigorous dynamical theory that maintains coherences throughout the relevant timescales. Recently we predicted[1] the potential to measure very small exchange interactions between spins through the formation of a bottleneck state, formed from a coherent singlet-triplet superposition, in spin-polarized transport oblique to a magnetic field. Spin-polarized scanning tunneling probes could reveal therefore the micro-eV exchange energies we have predicted between spin centers separated by up to 2 nm[2]. Similar sensitivities to the dipole electric field generated from a chromophore could be similarly detected by a single NV center, proving a new avenue for single-photon detection.[3] When quantum coherence can be maintained in the field excitation, such as for highly coherent magnons in small magnetic regions, the spin-magnon coupling could entangle NV centers separated by several microns[4].

Work in collaboration with D. R. Candido, G. D. Fuchs, N. J. Harmon, E. Johnston-Halperin, V. R. Kortan, S. R. McMillan and C. Sahin.

[1] S. R. McMillan, N. J. Harmon, and M. E. Flatté, arXiv:1907.05509 (2019); PRL in press.
[2] V. R. Kortan, C. Sahin, and M. E. Flatté, PRB 93, 220402(R) (2016).
[3] N. J. Harmon and M. E. Flatté, arXiv:1906.01800 (2019).
[4] D. R. Candido, G. D. Fuchs, E. Johnston-Halperin, and M. Flatté, Mater. Quantum Technol. in press. https://doi.org/10.1088/2633-4356/ab9a55