Control of valley dynamics in silicon quantum dots in the presence of an interface step

TL;DR

This paper investigates how a single-atom high interface step in silicon quantum dots affects valley qubit dynamics, enabling enhanced control and readout methods crucial for scalable quantum computing.

Contribution

It demonstrates that an interface step significantly influences valley qubit interactions, allowing for non-demolition readout and fast electrically driven control.

Findings

Interface step causes strong qubit-electric field interaction.

Non-demolition qubit readout via valley-to-charge conversion is possible.

Predicted gate times are shorter than relaxation and dephasing times.

Abstract

Recent experiments on silicon nanostructures have seen breakthroughs toward scalable, long-lived quantum information processing. The valley degree of freedom plays a fundamental role in these devices, and the two lowest-energy electronic states of a silicon quantum dot can form a valley qubit. In this work, we show that a single-atom high step at the silicon/barrier interface induces a strong interaction of the qubit and in-plane electric fields, and analyze the consequences of this enhanced interaction on the dynamics of the qubit. The charge densities of the qubit states are deformed differently by the interface step, allowing non-demolition qubit readout via valley-to-charge conversion. A gate-induced in-plane electric field together with the interface step enables fast control of the valley qubit via electrically driven valley resonance. We calculate single- and two-qubit gate times, as well as relaxation and dephasing times, and present predictions for the parameter range where the gate times can be much shorter than the relaxation time and dephasing is reduced.