Detecting ground-state degeneracy in many-body systems through qubit decoherence

TL;DR

This paper proposes a method using qubit decoherence to reliably detect ground-state degeneracy in many-body systems, validated through models including topological systems across various dimensions.

Contribution

It introduces a universal approach leveraging qubit decoherence to identify ground-state degeneracy, applicable to diverse many-body and topological systems.

Findings

Qubit decoherence varies significantly at band touching points.

Decoherence partially reflects degeneracy within energy bands.

Method validated across 1D, 2D, and 3D topological systems.

Abstract

By coupling with a qubit, we demonstrate that qubit decoherence can unambiguously detect the occurrence of ground-state degeneracy in many-body systems. We first demonstrate universality using the two-band model. Consequently, several exemplifications, focused on topological condensed matter systems in one, two, and three dimensions, are presented to validate our proposal. The key point is that qubit decoherence varies significantly when energy bands touch each other at the Fermi surface. In addition, it can partially reflect the degeneracy inside the band. This feature implies that qubit decoherence can be used for reliable diagnosis of ground-state degeneracy.