Double Quantum Dots as Detectors of High-Frequency Quantum Noise in Mesoscopic Conductors

TL;DR

This paper introduces a method using double quantum dots as tunable, frequency-resolving detectors for high-frequency quantum noise in mesoscopic conductors, capable of capturing vacuum and non-equilibrium fluctuations.

Contribution

It presents a novel measurement setup employing a double quantum dot to detect quantum noise across a wide frequency range, including vacuum fluctuations at low temperatures.

Findings

The inelastic current in the double quantum dot reflects the noise spectrum of the nearby conductor.

The setup can distinguish between equilibrium and non-equilibrium fluctuations.

Application to quantum point contact noise demonstrates the detector's effectiveness.

Abstract

We propose a measurement set-up for detecting quantum noise over a wide frequency range using inelastic transitions in a tunable two-level system as a detector. The frequency-resolving detector consists of a double quantum dot which is capacitively coupled to the leads of a nearby mesoscopic conductor. The inelastic current through the double quantum dot is calculated in response to equilibrium and non-equilibrium current fluctuations in the nearby conductor, including vacuum fluctuations at very low temperatures. As a specific example, the fluctuations across a quantum point contact are discussed.