Universal behavior of the Shannon mutual information in non-integrable self-dual quantum chains

TL;DR

This study tests a conjecture that the Shannon mutual information in ground states of conformally invariant quantum chains scales with the central charge, extending analysis to non-integrable models with new self-dual $Z(Q)$ symmetric chains.

Contribution

The paper introduces new non-integrable, self-dual $Z(Q)$ symmetric quantum chains and demonstrates that the mutual information conjecture holds for these models, regardless of integrability.

Findings

Mutual information scales with the central charge in non-integrable chains.

New $Z(Q)$ symmetric chains are critical and conformally invariant.

Conjectured mutual information behavior applies beyond integrable models.

Abstract

An existing conjecture states that the Shannon mutual information contained in the ground state wavefunction of conformally invariant quantum chains, on periodic lattices, has a leading finite-size scaling behavior that, similarly as the von Neumann entanglement entropy, depends on the value of the central charge of the underlying conformal field theory describing the physical properties. This conjecture applies whenever the ground state wavefunction is expressed in some special basis (conformal basis). Its formulation comes mainly from numerical evidences on exactly integrable quantum chains. In this paper the above conjecture was tested for several general non-integrable quantum chains. We introduce new families of self-dual $Z(Q)$ symmetric quantum chains ($Q=2,3,\ldots$). These quantum chains contain nearest neighbour as well next-nearest neighbour interactions (coupling constant $p$). In the cases $Q=2$ and $Q=3$ they are extensions of the standard quantum Ising and 3-state Potts chains, respectively. For $Q=4$ and $Q\geq 5$ they are extensions of the Ashkin-Teller and $Z(Q)$ parafermionic quantum chains. Our studies indicate that these models are interesting on their own. They are critical, conformally invariant, and share the same universality class in a continuous critical line. Moreover, our numerical analysis for $Q=2-8$ indicate that the Shannon mutual information exhibits the conjectured behaviour irrespective if the conformally invariant quantum chain is exactly integrable or not. For completeness we also calculated, for these new families of quantum chains, the two existing generalizations of the Shannon mutual information, which are based on the R\'enyi entropy and on the R\'enyi divergence.