Constructible reality condition of pseudo entropy via pseudo-Hermiticity

TL;DR

This paper explores the conditions under which pseudo entropy, a generalization of entanglement entropy, remains real by applying pseudo-Hermiticity, with implications for holography and quantum phase transitions.

Contribution

It introduces a pseudo-Hermitian framework to determine the reality conditions of pseudo entropy and constructs transition matrices with non-negative pseudo (Rényi) entropies.

Findings

Derived the general form of transition matrices with real or complex eigenvalues.

Constructed classes of transition matrices with non-negative pseudo entropy.

Connected the reality condition of pseudo entropy to Tomita-Takesaki modular theory.

Abstract

As a generalization of entanglement entropy, pseudo entropy is not always real. The real-valued pseudo entropy has promising applications in holography and quantum phase transition. We apply the notion of pseudo-Hermticity to formulate the reality condition of pseudo entropy. We find the general form of the transition matrix for which the eigenvalues of the reduced transition matrix possess real or complex pairs of eigenvalues. Further, we construct a class of transition matrices for which the pseudo (R\'enyi) entropies are non-negative. Some known examples which give real pseudo entropy in quantum field theories can be explained in our framework. Our results offer a novel method to generate the transition matrix with real pseudo entropy. Finally, we show the reality condition for pseudo entropy is related to the Tomita-Takesaki modular theory for quantum field theory.