Coherence of an Electronic Two-Level System under Continuous Charge Sensing by a Quantum Dot Detector

TL;DR

This study experimentally examines the quantum coherence of a double quantum dot system under continuous charge detection, revealing how detector-induced back-action causes decoherence and highlighting the need for more comprehensive theoretical models.

Contribution

It provides experimental measurements of back-action-induced decoherence in a double quantum dot and proposes a model linking decoherence to detector charge fluctuations.

Findings

Decoherence rate is approximately linearly proportional to the detector tunneling rate.

The measured decoherence exceeds the theoretical prediction by a factor of two.

Back-action effects significantly impact quantum coherence in charge sensing experiments.

Abstract

We investigate experimentally the quantum coherence of an electronic two-level system in a double quantum dot under continuous charge detection. The charge-state of the two-level system is monitored by a capacitively coupled single quantum dot detector that imposes a back-action effect to the system. The measured back-action is well described by an additional decoherence rate, approximately linearly proportional to the detector electron tunneling rate. We provide a model for the decoherence rate arising due to level detuning fluctuations induced by detector charge fluctuations. The theory predicts a factor of two lower decoherence rate than observed in the experiment, suggesting the need for a more elaborate theory accounting for additional sources of decoherence.