Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures

TL;DR

This paper investigates microwave dielectric losses at ultra-low temperatures and excitation energies, revealing excess loss in amorphous materials and analyzing the loss mechanisms using a two-level state defect model.

Contribution

It provides measured loss tangents for various dielectrics at millikelvin temperatures and near single-photon energies, with a theoretical analysis of resonator energy dissipation.

Findings

Excess microwave loss observed in amorphous dielectrics at low temperatures.

Loss behavior explained by two-level state defect model.

Theoretical analysis of resonator energy dissipation on multilayer substrates.

Abstract

The microwave performance of amorphous dielectric materials at very low temperatures and very low excitation strengths displays significant excess loss. Here, we present the loss tangents of some common amorphous and crystalline dielectrics, measured at low temperatures (T < 100 mK) with near single-photon excitation energies, using both coplanar waveguide (CPW) and lumped LC resonators. The loss can be understood using a two-level state (TLS) defect model. A circuit analysis of the half-wavelength resonators we used is outlined, and the energy dissipation of such a resonator on a multilayered dielectric substrate is considered theoretically.