Landau-Zener Transitions in Spin Qubit Encoded in Three Quantum Dots

TL;DR

This paper investigates the generation and control of an exchange spin qubit in three quantum dots using Landau-Zener transitions, comparing linear and triangular geometries for potential quantum computing applications.

Contribution

It introduces a method for coherent control of spin qubits in different quantum dot geometries using Landau-Zener transitions, highlighting the effects of system symmetry and size.

Findings

Triangular geometry allows easy qubit state generation due to symmetry.

Rabi oscillations enable coherent manipulation when one dot is smaller.

Linear geometry is easier to fabricate but complicates qubit control.

Abstract

We study generation and dynamics of an exchange spin qubit encoded in three coherently coupled quantum dots with three electrons. For two geometries of the system a linear and a triangular one, the creation and coherent control of the qubit states are performed by the Landau--Zener transitions. In the triangular case both the qubit states are equivalent and can be easily generated for particular symmetries of the system. If one of the dots is smaller than the others one can observe Rabi oscillations, that can be used for coherent manipulation of the qubit states. The linear system is easier to fabricate; however, then the qubit states are not equivalent, making qubit operations more difficult to control.