Theory of electrical readout of deep defect qubits in solids*

Paramagnetic color centers with deep levels in the gap are candidates to realize qubits in solids, in particular, those color centers that show spin-dependent fluorescence that can be employed to initialize and readout the electron spin of single color centers, first demonstrated for the nitrogen-vacancy (NV) center in diamond [1]. It has been shown [2] that optical excitation can also lead to ionization of NV center that is also spin dependent. The resultant carriers, i.e., the photocurrent can be collected that is the ground of photocurrent detected magnetic resonance (PDMR).
In my talk, I will show the power and significance of ab initio atomistic simulation techniques that can provide deep insight into the microscopic mechanisms behind the observed phenomena, and how it can be applied to optimize the conditions of qubit measurements. In particular, I will show how ab initio theory can explain the two-photon ionization of NV centre [3] that is the base of PDMR measurements. Intricate details of back ionization reveal the optical spinpolarization process in NV centre [4] under continuous green laser excitation. Theory predicted that two-color excitation will increase the signal-to-noise ratio of PDMR signal of NV center in diamond that was confirmed in experiment [5].
We will discuss very prospective deep color centers, divacancies in silicon carbide [6,7], what could be the experimental conditions to realize PDMR signal from these qubits in this technologically mature semiconductor.

[1] A. Gruber et al., Science 276, 2012-2014 (1997)
[2] E. Bourgeois et al., Nat. Com. 6, 8577 (2015)
[3] P. Siyushev et al., Phys. Rev. Lett. 110, 167402 (2013)
[4] G. Thiering and A. Gali, Phys. Rev. B 98, 085207 (2018)
[5] E. Bourgeois et al., Phys. Rev. B 95, 041402(R) (2017)
[6] A. Gali, phys. stat. sol. b 248, 1337 (2011)
[7] W. E. Koehl et al, Nature 479, 84 (2011)