Frustration of decoherence in $Y$-shaped superconducting Josephson networks

TL;DR

This paper explores how impurities in Y-shaped superconducting Josephson networks can lead to a stable phase that supports two-level quantum systems with frustrated entanglement, potentially enhancing quantum coherence.

Contribution

It introduces a new stable infrared fixed point in the phase diagram of Y-shaped Josephson networks, enabling the design of devices with improved quantum coherence.

Findings

Discovery of a new finite coupling stable infrared fixed point.

Support for two-level quantum systems with frustrated entanglement.

Potential for engineering superconducting devices with enhanced quantum coherence.

Abstract

We examine the possibility that pertinent impurities in a condensed matter system may help in designing quantum devices with enhanced coherent behaviors. For this purpose, we analyze a field theory model describing Y- shaped superconducting Josephson networks. We show that a new finite coupling stable infrared fixed point emerges in its phase diagram; we then explicitly evidence that, when engineered to operate near by this new fixed point, Y-shaped networks support two-level quantum systems, for which the entanglement with the environment is frustrated. We briefly address the potential relevance of this result for engineering finite-size superconducting devices with enhanced quantum coherence. Our approach uses boundary conformal field theory since it naturally allows for a field-theoretical treatment of the phase slips (instantons), describing the quantum tunneling between degenerate levels.