Controlled exchange interaction for quantum logic operations with spin qubits in coupled quantum dots

TL;DR

This paper investigates how controlled exchange interactions in coupled quantum dots can enable reliable spin swap operations for quantum computing, emphasizing the importance of smooth interaction changes.

Contribution

It introduces methods to control exchange interactions in quantum dots and analyzes their effects on spin swap efficiency for quantum logic operations.

Findings

Smoothly varying exchange interactions optimize spin swap times.

Jumps and spikes in interaction increase swap duration.

Proposed mechanisms to modify confinement potential improve control.

Abstract

A two-electron system confined in two coupled semiconductor quantum dots is investigated as a candidate for performing quantum logic operations on spin qubits. We study different processes of swapping the electron spins by controlled switching on/off the exchange interaction. The resulting spin swap corresponds to an elementary operation in quantum information processing. We perform a direct time evolution simulations of the time-dependent Schroedinger equation. Our results show that -- in order to obtain the full interchange of spins -- the exchange interaction should change smoothly in time. The presence of jumps and spikes in the corresponding time characteristics leads to a considerable increase of the spin swap time. We propose several mechanisms to modify the exchange interaction by changing the confinement potential profile and discuss their advantages and disadvantages.