Quantum simulation with dopant atoms in a semiconductor

Joe Salfi, Jan A. Mol, Rajib Rahman, Gerhard Klimeck, Michelle Yvonne Simmons, Lloyd C. L. Hollenberg, Sven M. J. Rogge

Published Jul 22, 2015• 1 citation

Abstract

In quantum simulation, many-body phenomena are probed in controllable quantum systems. Recently, single-site measurements in cold-atom quantum simulations of bosons revealed previously hidden local correlations. However, interacting Fermi-Hubbard systems, connected to canonical open many-body physics problems, are more difficult to simulate using cold atoms. To date, only ensemble measurements have been achieved, while the required single-site measurements and cooling remain formidable challenges. Here we demonstrate quantum simulation of a two-impurity Fermi system using subsurface Coulomb-coupled dopant atoms in silicon. Quasiparticle tunneling maps of individually identifiable coupled-spin states were obtained by scanning tunneling spectroscopy, at low effective temperatures, and resolving individual dopants. From the maps we quantified the two-body probability amplitudes and the entanglement of the overlapping (indistinguishable) fermions, enabling quantum simulation of a thought-experiment on a stretched covalent bond. Entanglement, determined by spin and orbital components, was found to increase with increasing dopant displacement, as interactions overcome tunneling, localizing spin. Looking ahead, we extracted the effective Hubbard interaction strength, which follows a hydrogenic, separation-tunable trend appropriate to simulate emergent Fermi-Hubbard phenomena in larger sets of dopants. These results pave the way for quantum simulation of larger scale correlated Fermi-Hubbard systems, exploiting atomic-scale fabrication to engineer interactions atom-by-atom.

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