Non-Perturbative Topological Gadgets for Many-Body Coupling

TL;DR

This paper introduces non-perturbative topological gadgets that enable high-order multi-body interactions in quantum systems, leveraging defect subspaces and topological properties to overcome limitations of traditional perturbative methods.

Contribution

It presents a novel class of non-perturbative gadgets utilizing topological defect subspaces to generate multi-body interactions, expanding beyond perturbative approaches.

Findings

Demonstrates how topological defects can produce multi-body couplings

Shows the potential for complex gadget constructions in ice-like systems

Provides conceptual simplicity with domain-wall defect-based interactions

Abstract

Continuous-time quantum hardware implementations generally lack the native capability to implement high-order terms that would facilitate efficient compilation of quantum algorithms. This limitation has, in part, motivated the development of perturbative gadgets -- multi-qubit constructions used to effect a desired Hamiltonian using engineered low-energy subspaces of a larger system constructed using simpler, usually two-body, primitives. In this work, we demonstrate how a class of non-perturbative gadgets can produce high-order multi-body interactions by taking advantage of the odd-even properties of topological defect subspaces. The simplest example is based on domain-wall defects forming an effective Ising spin-chain based on three-body coupling with linear connectivity, alongside three-, or five-body driving terms depending on the intended use. Although this will be the main focus of the paper due to conceptual simplicity, there exist systems constructed with only two-body couplings where the boundaries determine whether there are an odd or even number of defects, namely ice-like systems which may yield more complex gadget-like constructions.