Quantum two level systems and Kondo-like traps as possible sources of decoherence in superconducting qubits

TL;DR

This paper investigates the sources of decoherence in superconducting qubits, proposing that electron traps with strong Coulomb repulsion in the Josephson barrier are likely primary noise contributors, rather than two-level systems in the insulator.

Contribution

It introduces the idea that electron traps with large Coulomb repulsion are the main source of decoherence, challenging the previous focus on two-level systems.

Findings

Two-level systems are unlikely to be the dominant noise source in small qubits.

Electron traps with large Coulomb repulsion produce noise consistent with experimental data.

The temperature dependence of noise supports the electron trap hypothesis.

Abstract

We discuss the origin of decoherence in Josephson junction qubits. We find that two level systems in the surrounding insulator cannot be the dominant source of noise in small qubits. We argue that electron traps in the Josephson barrier with large Coulomb repulsion would give noise that agrees both in magnitude and in temperature dependence with experimental data.