U(1) Fields from Qubits: an Approach via D-theory Algebra

TL;DR

This paper introduces a novel quantum computing framework for lattice gauge theories, replacing traditional gauge links with fermionic qubits, and demonstrates its potential for simulating various Abelian and non-Abelian fields.

Contribution

It develops a general formalism using D-theory for quantum link models, enabling efficient simulation of lattice gauge theories with qubits, and extends the approach to non-Abelian groups.

Findings

Framework for $U(1)$ fields using qubits

Progress towards non-Abelian gauge theories

Potential for simulating lattice QCD and sigma models

Abstract

A new quantum link microstructure was proposed for the lattice quantum chromodynamics (QCD) Hamiltonian, replacing the Wilson gauge links with a bilinear of fermionic qubits, later generalized to D-theory. This formalism provides a general framework for building lattice field theory algorithms for quantum computing. We focus mostly on the simplest case of a quantum rotor for a single compact $U(1)$ field. We also make some progress for non-Abelian setups, making it clear that the ideas developed in the $U(1)$ case extend to other groups. These in turn are building blocks for $1 + 0$-dimensional ($1 + 0$-D) matrix models, $1 + 1$-D sigma models and non-Abelian gauge theories in $2+1$ and $3+1$ dimensions. By introducing multiple flavors for the $U(1)$ field, where the flavor symmetry is gauged, we can efficiently approach the infinite-dimensional Hilbert space of the quantum $O(2)$ rotor with increasing flavors. The emphasis of the method is on preserving the symplectic algebra exchanging fermionic qubits by sigma matrices (or hard bosons) and developing a formal strategy capable of generalization to $SU(3)$ field for lattice QCD and other non-Abelian $1 + 1$-D sigma models or $3 +3$-D gauge theories. For $U(1)$, we discuss briefly the qubit algorithms for the study of the discrete $1+1$-D Sine-Gordon equation.