Atomistic simulations of adiabatic coherent electron transport in triple donor systems

TL;DR

This paper demonstrates through large-scale atomistic simulations that coherent tunneling adiabatic passage (CTAP) can be effectively implemented in silicon triple donor systems, enabling robust quantum state transfer within practical timescales.

Contribution

It provides the first atomistic simulation evidence of CTAP in realistic solid-state systems, combining tight-binding models with gate control analysis for triple donors in silicon.

Findings

CTAP can transfer electrons in silicon donors within 23 ps

Simulations confirm the existence of a CTAP pathway in realistic conditions

Gate control and cross-talk effects are critical for CTAP implementation

Abstract

A solid-state analogue of Stimulated Raman Adiabatic Passage can be implemented in a triple well solid-state system to coherently transport an electron across the wells with exponentially suppressed occupation in the central well at any point of time. Termed coherent tunneling adiabatic passage (CTAP), this method provides a robust way to transfer quantum information encoded in the electronic spin across a chain of quantum dots or donors. Using large scale atomistic tight-binding simulations involving over 3.5 million atoms, we verify the existence of a CTAP pathway in a realistic solid-state system: gated triple donors in silicon. Realistic gate profiles from commercial tools were combined with tight-binding methods to simulate gate control of the donor to donor tunnel barriers in the presence of cross-talk. As CTAP is an adiabatic protocol, it can be analyzed by solving the time independent problem at various stages of the pulse - justifying the use of time-independent tight-binding methods to this problem. Our results show that a three donor CTAP transfer, with inter-donor spacing of 15 nm can occur on timescales greater than 23 ps, well within experimentally accessible regimes. The method not only provides a tool to guide future CTAP experiments, but also illuminates the possibility of system engineering to enhance control and transfer times.