Locally tunable disorder and entanglement in the one-dimensional plaquette orbital model

TL;DR

This paper introduces a one-dimensional plaquette orbital model with a ladder topology, analyzing its ground state, excitations, and entanglement properties, revealing localized entanglement islands that could be relevant for quantum computing.

Contribution

It presents a novel 1D plaquette orbital model, maps it to an effective spin model, and investigates its quantum effects, entanglement, and potential for quantum computing applications.

Findings

Quantum effects are short-range in the model.

Ground state energy and gap estimated up to 12 dimers.

Localized entanglement islands are found in excited states.

Abstract

We introduce a one-dimensional plaquette orbital model with a topology of a ladder and alternating interactions between $x$ and $z$ pseudospin components along both the ladder legs and on the rungs. We show that it is equivalent to an effective spin model in a magnetic field, with spin dimers that replace plaquettes and are coupled along the chain by three-spin interactions. Using perturbative treatment and mean field approaches with dimer correlations we study the ground state spin configuration and its defects in the lowest excited states. By the exact diagonalization approach we find that the quantum effects in the model are purely short-range and we get estimated values of the ground state energy and the gap in the thermodynamic limit from the system sizes up to $L=12$ dimers. Finally, we study a class of excited states with classical-like defects accumulated in the central region of the chain to find that in this region the quantum entanglement measured by the mutual information of neighboring dimers is locally increased and coincides with disorder and frustration. Such islands of entanglement in otherwise rather classical system may be of interest in the context of quantum computing devices.