Loss of quantum coherence due to non-stationary glass fluctuations

TL;DR

This paper investigates how non-stationary glass fluctuations, caused by tunneling two-level systems, lead to quantum decoherence in solid state qubits at low temperatures, highlighting the dominance of non-thermal effects.

Contribution

It introduces a detailed analysis of non-stationary glass fluctuations' impact on qubit dephasing, emphasizing the significance of slow fluctuators at low temperatures.

Findings

Non-stationary glass fluctuations can dominate thermal effects at low temperatures.

Fluctuating electromagnetic fields from tunneling systems cause qubit dephasing.

Strategies to minimize non-thermal dephasing effects are discussed.

Abstract

Low-temperature dynamics of insulating glasses is dominated by a macroscopic concentration of tunneling two-level systems (TTLS). The distribution of the switching/relaxation rates of TTLS is exponentially broad, which results in non-equilibrium state of the glass at arbitrarily long time-scales. Due to the electric dipolar nature, the switching TTLS generate fluctuating electromagnetic fields. We study the effect of the non-thermal slow fluctuators on the dephasing of a solid state qubit. We find that at low enough temperatures, non-stationary contribution can dominate the stationary (thermal) one, and discuss how this effect can be minimized.