Atom-Based Silicon Devices for Quantum Computing and Analog Quantum Simulation

NIST is using atomically precise fabrication to develop devices for use in quantum information
processing. We are using hydrogen-based scanning probe lithography for deterministic
placement of individual dopant atoms with atomically aligned gates to fabricate single/few
atom transistors, few-donor/quantum dot devices for spin manipulation, and arrayed few-
donor devices for quantum materials and analog quantum simulation research.
I will discuss tunnel coupling in donor-dot devices where the tunnel gap is varied at the atomic
scale as well as analysis of few atom transistors used to estimate parametric inputs to the
Hubbard model such as onsite energies and tunnel coupling. We then describe STM-fabrication
and quantum transport measurement of arrays of few atom clusters ranging from 1x2 double
dots to a multi-gate 3×3 dot array to explore the rich Hubbard physics of quantum dot-arrays.
Using the Si (100)2x1 surface reconstruction as an atomic ruler, we vary the tunnel coupling
between nearby dots from a weakly to strongly coupled regime. Using an extended Hubbard
model we explore the impact of site-by-site disorder on charge occupation, the spatial
distribution of the eigenstates, the Anderson Mott transition, and the Hubbard band structure.
We identify resonant and inelastic conductance paths and extract neighboring and long-
distance coherent tunnel coupling strength. We quantify the electron addition energy
spectrum through Coulomb blockade and charge stability analysis and demonstrate tuning of
the energy spectrum using gate potential gradients.