ENCORE: An Extended Contractor Renormalization algorithm

TL;DR

This paper introduces ENCORE, an extended version of the CORE algorithm, enabling the derivation of effective models with non-tensor product Hilbert spaces, useful for modeling exotic quantum systems and designing quantum devices.

Contribution

The paper extends the CORE method to handle effective models with non-tensor product Hilbert spaces, broadening its applicability.

Findings

Enables derivation of complex effective models beyond tensor product spaces

Facilitates modeling of low-energy exotic quantum systems

Guides the design of quantum devices

Abstract

Contractor renormalization (CORE) is a real-space renormalization-group method to derive effective Hamiltionians for microscopic models. The original CORE method is based on a real-space decomposition of the lattice into small blocks and the effective degrees of freedom on the lattice are tensor products of those on the small blocks. We present an extension of the CORE method that overcomes this restriction. Our generalization allows the application of CORE to derive arbitrary effective models whose Hilbert space is not just a tensor product of local degrees of freedom. The method is especially well suited to search for microscopic models to emulate low-energy exotic models and can guide the design of quantum devices.