Stabilisers as a design tool for new forms of Lechner-Hauke-Zoller Annealer

TL;DR

This paper introduces a stabiliser-based framework for designing quantum annealing architectures, enabling flexible connectivity and high-order interactions while potentially simplifying physical implementation and improving annealing performance.

Contribution

It provides a unified stabiliser formulation for the Lechner-Hauke-Zoller approach and variants, including new layouts with simplified constraints and connectivity options.

Findings

Supports various connectivity layouts including triangular and sparse arrangements.

Enables realization of high-order logical terms in 2D layouts efficiently.

Preliminary simulations suggest improved energy gap properties in some variants.

Abstract

In a recent paper Lechner, Hauke and Zoller (LHZ) described a means to translate a Hamiltonian of $N$ spin-$\frac{1}{2}$ particles with 'all-to-all' interactions into a larger physical lattice with only on-site energies and local parity constraints. LHZ used this mapping to propose a novel form of quantum annealing. Here we provide a stabiliser-based formulation within which we can describe both this prior approach and a wide variety of variants. Examples include a triangular array supporting all-to-all connectivity, and moreover arrangements requiring only $2N$ or $N\log N$ spins but providing interesting bespoke connectivities. Further examples show that arbitrarily high order logical terms can be efficiently realised, even in a strictly 2D layout. Our stabilisers can correspond to either even-parity constraints, as in the LHZ proposal, or as odd-parity constraints. Considering the latter option applied to the original LHZ layout, we note it may simplify the physical realisation since the required ancillas are only spin-$\frac{1}{2}$ systems (i.e. qubits, rather than qutrits) and moreover the interactions are very simple. We make a preliminary assessment of the impact of this design choices by simulating small (few-qubit) systems; we find some indications that the new variant may maintain a larger minimum energy gap during the annealing process.