Fast electron thermometry towards ultra-sensitive calorimetric detection

TL;DR

This paper presents a radiofrequency thermometry technique on a micrometer-sized metallic island operating below 100 mK, achieving high sensitivity and fast thermal relaxation measurements for potential quantum calorimetry applications.

Contribution

The work introduces a novel RF thermometry device with high sensitivity and fast response, suitable for integration into superconducting circuits for quantum thermodynamics.

Findings

Achieved 90 μK/Hz^1/2 noise-equivalent temperature

Measured electron thermal relaxation time of ~100 μs

Demonstrated potential for ultra-sensitive calorimetric detection

Abstract

We demonstrate radiofrequency thermometry on a micrometer-sized metallic island below 100 mK. Our device is based on a normal metal-insulator-superconductor tunnel junction coupled to a resonator with transmission readout. In the first generation of the device, we achieve 90 {\mu}K/Hz^1/2 noise-equivalent temperature with 10 MHz bandwidth. We measure the thermal relaxation time of the electron gas in the island, which we find to be of the order of 100 {\mu}s. Such a calorimetric detector, upon optimization, can be seamlessly integrated into superconducting circuits, with immediate applications in quantum-thermodynamics experiments down to single quanta of energy.