Evidence of two-dimensional macroscopic quantum tunneling of a current-biased DC-SQUID

TL;DR

This paper provides experimental evidence of two-dimensional macroscopic quantum tunneling in a current-biased DC-SQUID, showing flux-dependent escape probabilities at low temperatures that deviate from traditional 1D models.

Contribution

The study demonstrates that the escape dynamics of a hysteretic DC-SQUID are better explained by a two-dimensional MQT model rather than the conventional one-dimensional approach.

Findings

Escape probability is flux-dependent at low temperatures.

Data aligns with 2D MQT predictions, not 1D.

Near zero flux, results confirm recent MQT observations.

Abstract

The escape probability out of the superconducting state of a hysteretic DC-SQUID has been measured at different values of the applied magnetic flux. At low temperature, the escape current and the width of the probability distribution are temperature independent but they depend on flux. Experimental results do not fit the usual one-dimensional (1D) Macroscopic Quantum Tunneling (MQT) law but are perfectly accounted for by the two-dimensional (2D) MQT behaviour as we propose here. Near zero flux, our data confirms the recent MQT observation in a DC-SQUID \cite{Li02}.