Description
Fabrication of large-scale quantum computer devices comprised of donor atoms in silicon could employ some of the standard techniques of the semiconductor device industry. Exploiting the promise of long coherence times of electron and nuclear spins in enriched silicon requires ordered arrays of donor qubits [1] coupled by gates in a silicon substrate depleted in the $^{29}$Si isotope (nuclear spin $I=1/2$). By employing our novel ion beam method [2], $^{29}$Si was depleted from 47,000 ppm to below 10 ppm so that the corresponding spin bath does not couple to the qubit spins [2]. We have explored the large parameter space that requires optimisation for device construction guided by the Breit-Rabi formalism for the Hamiltonian in the low magnetic field regime ($B<100 G$) where the Zeeman term is comparable in magnitude to the hyperfine term. With application of the appropriate selection rules, the energies of donor spin magnetic resonances can be determined. For $^{123}$Sb donors ($I=7/2$) there are many overlaying resonances as a function of magnetic field, $B$, and transition frequency, $f$ [3]. We have identified suitable domains in this complicated landscape where clock transitions [4] are identified as parameter space points where $f(B)$ goes to zero and long coherence times are expected. We also investigate the presence of lattice defects and dangling bonds that require process optimisation to improve the qubit lifetimes.
References
[1] A. Jakob, et al., Adv. Mat. 36 (2024)
[2] R. Acharya, et al., Comm. Mat. 5:57 (2024)
[3] A. Morello, et al., Nat. Commun. 15:1380 (2024)
[4] R. Acharya, et al., arxiv.org/abs/2604.24090, Phys. Rev. Mat. (2026)
| I am the presenting author | Yes |
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