Measurements of 1/ f noise in Josephson junctions at zero voltage: Implications for decoherence in superconducting quantum bits

TL;DR

This paper measures 1/f critical current noise in Josephson junctions at zero voltage, revealing its potential impact on decoherence in superconducting qubits, and finds consistent noise levels across different measurement modes.

Contribution

It provides the first direct measurement of 1/f noise at zero voltage in Josephson junctions, relevant for qubit decoherence studies.

Findings

1/f noise magnitude is similar in zero and nonzero voltage regimes

Critical current fluctuations could limit qubit coherence

Measurements confirm noise levels are consistent across methods

Abstract

Critical current fluctuations with a 1/ f spectral density (f is frequency) are potentially a limiting source of intrinsic decoherence in superconducting quantum bits (qubits) based on Josephson tunnel junctions. Prior measurements of this noise were made at nonzero voltages whereas qubits are operated in the zero voltage state. We report measurements of 1/ f noise in a dc superconducting quantum interference device first, coupled to a resonant tank circuit and operated in a dispersive mode at zero voltage, and, second, operated conventionally with a current bias in the voltage regime. Both measurements yield essentially the same magnitude of critical current 1/ f noise.