Quantum and thermal fluctuations in the dynamics of a resistively and capacitively shunted Josephson junction

TL;DR

This paper models the combined effects of quantum and thermal fluctuations on phase and voltage dynamics in a resistively and capacitively shunted Josephson junction, revealing how resistance and temperature influence long-term correlations.

Contribution

It provides a theoretical analysis of phase and voltage correlations considering both quantum and thermal noise in Josephson junctions, highlighting the impact of resistance and temperature.

Findings

Asymptotic correlations depend on resistance due to quantum effects.

Higher temperatures lead to faster decay of coherence.

External current shifts and amplifies deterministic contributions.

Abstract

We theoretically investigate the phase and voltage correlation dynamics, which includes both the deterministic contribution and stochastic fluctuations, under a current noise generated by a resistor including thermal and quantum fluctuations in a resistively and capacitively shunted Josephson junction. An external current is found to shift and intensify the deterministic contributions in phase and voltage. In addition to effects of external current, we observe the relaxation of autocorrelation functions of phase and voltage, which includes the variances due to the current noise, to finite values in the long-time limit. In particular, we find that the asymptotic correlations depend on the resistance as a consequence of quantum effects. We also find an earlier decay of coherence at a higher temperature in which thermal fluctuations dominate over quantum ones. These theoretical predictions can be tested in the next future experiments.