Intrinsic phonon decoherence and quantum gates in coupled lateral quantum dot charge qubits

TL;DR

This paper investigates intrinsic phonon-induced decoherence and the performance of quantum gates in coupled lateral quantum dot charge qubits, highlighting how decoherence affects gate quality and proposing improvements.

Contribution

It introduces a detailed decoherence model for coupled charge qubits, analyzing how local and collective phonon interactions impact gate fidelity and suggesting methods to enhance performance.

Findings

Decoherence is limited by super-Ohmic phonon spectrum.

Gate quality is constrained by single-qubit Hadamard gates.

Weak tunnel coupling in double dots improves gate performance.

Abstract

Recent experiments by Hayashi et al. [Phys. Rev. Lett. 91, 226804 (2003)] demonstrate coherent oscillations of a charge quantum bit (qubit) in laterally defined quantum dots. We study the intrinsic electron-phonon decoherence and gate performance for the next step: a system of two coupled charge qubits. The effective decoherence model contains properties of local as well as collective decoherence. Decoherence channels can be classified by their multipole moments, which leads to different low-energy spectra. It is shown that due to the super-Ohmic spectrum, the gate quality is limited by the single-qubit Hadamard gates. It can be significantly improved, by using double-dots with weak tunnel coupling.