https://www.sciencedaily.com/releases/2020/05/200511092920.htm

Our collaborators at NIST, led by Rick Silver, are making huge progress towards developing a robust, reliable process for atomic-scale dopant-based devices. They have published several papers recently, particularly:

J. Wyrick et al., “Atom by Atom Fabrication of Single and Few Dopant Quantum Devices”, Advanced Functional Matls., Dec. 2019. DOI: 10.1002/adfm.201903475. 

X. Wang et al., “Atomic-scale control of Tunnel Coupling in Donor-based Devices”, Comm. Physics, Nature Research J., May 11, 2020. DOI: 10.1038/s42005-020-0343-1

From the press release, “The NIST researchers demonstrated for the first time the exponential scaling of the tunneling resistance on the tunnel gap as it is varied from 7 dimer rows to 16 dimer rows. They showed the capability to reproducibly pattern devices with atomic precision and a donor-based fabrication process where atomic scale changes in the patterned tunnel gap resulted in the expected changes in the tunneling rates.”

Also see: http://quantumhermit.com/particles-trapped-in-twisted-materials-and-quantum-fingerprints/