# Millikelvin measurements of permittivity and loss tangent of lithium niobate

## TL;DR

This paper reports precise measurements of lithium niobate's permittivity and loss tangent at millikelvin temperatures, crucial for quantum and microwave applications, using a superconducting cavity at 7 GHz.

## Contribution

It provides the first highly accurate characterization of lithium niobate's dielectric properties at millikelvin temperatures using a resonant method.

## Key findings

- Permittivity tensor measured at 50 mK
- Loss tangent characterized at millikelvin temperatures
- Enhanced accuracy over previous measurements

## Abstract

Lithium Niobate is an electro-optic material with many applications in microwave signal processing, communication, quantum sensing, and quantum computing. In this letter, we present findings on evaluating the complex electromagnetic permittivity of lithium niobate at millikelvin temperatures. Measurements are carried out using a resonant-type method with a superconducting radio-frequency (SRF) cavity operating at 7 GHz and designed to characterize anisotropic dielectrics. The relative permittivity tensor and loss tangent are measured at 50 mK with unprecedented accuracy.