Enhanced Coherence of a Quantum Doublet Coupled to Tomonaga-Luttinger Liquid Leads

TL;DR

This paper demonstrates that a tetrahedral qubit coupled to Tomonaga-Luttinger liquid leads can form a robust quantum doublet phase, resilient to noise and decoherence, with potential for practical quantum computing implementations.

Contribution

It introduces a new stable phase characterized by a quantum doublet arising from a tetrahedral Josephson junction network coupled to Luttinger liquid leads, analyzed via boundary field theory.

Findings

Emergence of a stable quantum doublet phase.

Robustness against noise and decoherence.

Feasibility of experimental realization with current technology.

Abstract

We use boundary field theory to describe the phases accessible to a tetrahedral qubit coupled to Josephson junction chains acting as Tomonaga-Luttinger liquid leads. We prove that, in a pertinent range of the fabrication and control parameters, an attractive finite coupling fixed point emerges due to the geometry of the composite Josephson junction network. We show that this new stable phase is characterized by the emergence of a quantum doublet which is robust not only against the noise in the external control parameters (magnetic flux, gate voltage) but also against the decoherence induced by the coupling of the tetrahedral qubit with the superconducting leads. We provide protocols allowing to read and to manipulate the state of the emerging quantum doublet and argue that a tetrahedral Josephson junction network operating near the new finite coupling fixed point may be fabricated with today's technologies.