Dielectric Loss due to Charged-Defect Acoustic Phonon Emission

Abstract

The coherence times of state-of-the-art superconducting qubits are limited by bulk dielectric loss, yet the microscopic mechanism leading to this loss is unclear. Here we propose that the experimentally observed loss can be attributed to the presence of charged defects that enable the absorption of electromagnetic radiation by the emission of acoustic phonons. Our explicit derivation of the absorption coefficient for this mechanism allows us to derive a loss tangent of $7.2\times 10^{-9}$ for Al${}_2$O${}_3$, in good agreement with recent high-precision measurements [A. P. Read et al., Phys. Rev. Appl. 19, 034064 (2023)]. We also find that for temperatures well below ~0.2 K, the loss should be independent of temperature, also in agreement with observations. Our investigations show that the loss per defect depends mainly on properties of the host material, and a high-throughput search suggests that diamond, cubic BN, AlN, and SiC are optimal in this respect.

References in corpus (6)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
• Disentangling Losses in Tantalum Superconducting Circuits
• Role of carbon and hydrogen in limiting $n$-type doping of monoclinic (Al${}_x$Ga${}_{1-x}$)${}_2$O${}_3$
• Precision measurement of the microwave dielectric loss of sapphire in the quantum regime with parts-per-billion sensitivity
• Acceptor-induced bulk dielectric loss in superconducting circuits on silicon

Cited by in corpus (1)

• Impact of Absorption due to Zero-Field Splitting on Loss in Dielectrics: A Case Study in Sapphire