Theory of two-dimensional macroscopic quantum tunneling in YBa$_2$ Cu$_3$ O$_{7-\delta}$ Josephson junctions coupled to an LC circuit

TL;DR

This paper provides a theoretical analysis of thermal activation and macroscopic quantum tunneling in YBCO Josephson junctions coupled to an LC circuit, revealing the importance of this coupling in quantum dynamics and qubit applications.

Contribution

It introduces a two-dimensional potential model for the junction-LC system and analytically calculates escape rates, aligning well with experimental data.

Findings

Significant suppression of MQT rate at zero temperature.

Temperature dependence of escape rate across the crossover region.

Excellent agreement with recent experimental measurements.

Abstract

We investigate classical thermal activation (TA) and macroscopic quantum tunneling (MQT) for a YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) Josephson junction coupled to an LC circuit theoretically. Due to the coupling between the junction and the LC circuit, the macroscopic phase dynamics can be described as the escape process of a fictitious particle with an anisotropic mass moving in a two-dimensional potential. We analytically calculate the escape rate including both the TA and MQT regime by taking into account the peculiar dynamical nature of the system. In addtion to large suppression of the MQT rate at zero temperature, we study details of the temperature dependece of the escape rate across a crossover region. These results are in an excellent agreement with recent experimental data for the MQT and TA rate in a YBCO biepitaxial Josephson junction. Therefore the coupling to the LC circuit is essential in understanding the macroscopic quantum dynamics and the qubit operation based on the YBCO biepitaxial Josephson junctions.