The Reflected Entanglement Spectrum for Free Fermions

TL;DR

This paper studies the reflected entanglement spectrum for free fermions in 1+1 dimensions, revealing its potential to extract physical data from ground states by analyzing the spectrum derived from the correlation functions.

Contribution

It introduces a method to compute the reflected entanglement spectrum directly in the continuum for free fermions, including analytical and numerical analysis in various limits.

Findings

Spectrum approaches thermal density matrix when intervals nearly touch

Reflected entanglement spectrum can be extracted from ground state wave functions

Method applicable directly in continuum theory for free fermions

Abstract

We consider the reflected entropy and the associated entanglement spectrum for free fermions reduced to two intervals in 1+1 dimensions. Working directly in the continuum theory the reflected entropy can be extracted from the spectrum of a singular integral equation whose kernel is determined by the known free fermion modular evolved correlation function. We find the spectrum numerically and analytically in certain limits. For intervals that almost touch the reflected entanglement spectrum approaches the spectrum of the thermal density matrix. This suggests that the reflected entanglement spectrum is well suited to the task of extracting physical data of the theory directly from the ground state wave function.