Acoustic decoherence of flux qubits

TL;DR

This paper investigates how thermal phonons cause decoherence in flux qubits, providing parameter-free rates that depend on qubit size and phonon wavelength, with implications for qubit operation temperatures and quality factors.

Contribution

It offers a parameter-free theoretical analysis of acoustic decoherence in flux qubits, highlighting size-dependent effects and temperature limits.

Findings

Decoherence rates depend on qubit size and phonon wavelength.

Thermal phonons limit small qubit operation to 10-20 K.

Large qubits experience significant acoustic decoherence at all temperatures.

Abstract

Decoherence of a flux qubit due to inelastic scattering of thermal phonons by the qubit is studied. The computed decoherence rates contain no unknown constants and are expressed entirely in terms of measurable parameters of the qubit. The answer depends strongly on the size of the qubit as compared to the wavelength of phonons of frequency corresponding to the tunnel splitting of the qubit. Thermal phonons set the upper limit on the operating temperature of a small qubit at around 10-20 K. For large qubits acoustic decoherence due to one phonon processes should be taken into account at any temperature when a high quality factor is desired.