Perturbative analysis of topological entanglement entropy from conditional independence

TL;DR

This paper analyzes the stability of topological entanglement entropy under perturbations using conditional independence, providing bounds based on energy gap and subsystem size, and extends results to finite temperature stabilizer models.

Contribution

It introduces a perturbative framework leveraging conditional independence to bound changes in topological entanglement entropy for quantum double and Levin-Wen models.

Findings

Bound on first order perturbation decreases superpolynomially with subsystem size.

Finite temperature stability proven for stabilizer models under certain conditions.

Stronger than strong subadditivity statement for entropy in stabilizer models.

Abstract

We use the structure of conditionally independent states to analyze the stability of topological entanglement entropy. For the ground state of quantum double or Levin-Wen model, we obtain a bound on the first order perturbation of topological entanglement entropy in terms of its energy gap and subsystem size. The bound decreases superpolynomially with the size of the subsystem, provided the energy gap is nonzero. We also study the finite temperature stability of stabilizer models, for which we prove a stronger statement than the strong subadditivity of entropy. Using this statement and assuming i) finite correlation length ii) small conditional mutual information of certain configurations, first order perturbation effect for arbitrary local perturbation can be bounded. We discuss the technical obstacles in generalizing these results.