Description
A large-scale quantum computer employing dopants in silicon requires a low background spin bath to prolong coherent quantum states. This presentation reviews our progress optimising the materials for this goal. We show that high fluence 28-Si ion irradiation of natural silicon depletes the problematic nuclear spin I=½ 29-Si isotope from 47,000 parts per million (ppm) to ~2 ppm. At this extreme depletion there is, on average, less than one 29-Si atom within the Bohr radius of the donor electrons. We have demonstrated 2.3 ppm residual 29-Si by employing focused 45 keV 28-Si ion beams with a fluence of ~1x1019/cm2 [1]. We have also found by using a broad negative ion beam in a conventional implanter that the same depletion is achieved with much less fluence [2]. We have built electrically detected magnetic resonance devices to measure the donor spin resonances of ion implanted two million donor ensembles and have demonstrated clock transitions that are insensitive to magnetic noise in 75-As [3]. The next step is to repeat this experiment highly enriched silicon epitaxial layers with directed implanted arrays of 123-Sb donors [4] in which robust logical quantum states can be encoded on the I=7/2 nuclear spin [5]. This addresses the first challenge of constructing of a large-scale million qubit device in the materials of choice for the classical semiconductor industry.
References
[1] R. Acharya, et al., Comm. Mat. 5:57 (2024)
[2] S.Q. Lim, et al., Phys. Rev. Mat. 9, 076202 (2025)
[3] R. Acharya, et al., arxiv.org/abs/2604.24090, Phys. Rev. Mat. (2026)
[4] A. Jakob, et al., Adv. Mat. 36 (2024)
[5] X. Yu, et al, Nature Physics, 21, 362-367 (2025)
| I am the presenting author | Yes |
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