Phonon influence on the measurement of spin states in double quantum dots using the quantum point contact

TL;DR

This paper investigates how phonon scattering affects the measurement of spin states in double quantum dots, revealing that phonons can obscure differences between singlet and triplet states, impacting measurement reliability.

Contribution

It demonstrates that phonon interactions can suppress distinguishable signals in spin state measurements, highlighting a critical factor in quantum dot spin readout accuracy.

Findings

Phonon relaxation suppresses transitions to doubly occupied singlet states.

Coupling to phonons reduces the distinguishability between singlet and triplet states.

Measurement validity is compromised due to phonon-induced noise masking spin state differences.

Abstract

We study the influence of phonon scattering on the single-triplet measurement of two-electron spin states in a double quantum dot doped with two electrons. We point out that at low temperatures phonon-induced relaxation to the ground state suppresses transitions to doubly occupied singlet states which are the source of detectable current fluctuations in this measurement scheme. Thus, for a relatively strong electron-phonon interaction present in the system, the two configurations display the same noise characteristics. In this way, coupling to phonons reduces the distinguishability between the singlet and triplet configurations. Under such conditions, the measurement scheme is no longer valid even though the temporal characteristics of the measurement process and measurement- induced localization are essentially unchanged.