Physicality oracle for SU(3) Loop-String-Hadron dynamics: a digital quantum circuit

TL;DR

This paper develops a quantum circuit oracle to verify gauge-invariance constraints in a quantum simulation of SU(3) lattice gauge theory, improving efficiency and maintaining physicality in the simulation.

Contribution

It introduces a quantum oracle for checking local gauge constraints in SU(3) lattice gauge theory using the Loop-String-Hadron formulation, reducing qubit requirements.

Findings

The LSH basis reduces qubit count compared to IRREP basis.

The oracle efficiently checks local gauge constraints during quantum simulation.

The approach maintains gauge invariance and addresses noise-induced constraint violations.

Abstract

Within the aim of understanding quantum chromodynamics through simulation, an increasingly studied approach is that of quantum computation and simulation. Challenges exist in encoding the minimal and physical degrees of freedom for a non-Abelian gauge theory and maintaining physical or gauge-invariant dynamics in a simulation. In this work, the Loop-String-Hadron (LSH) formulation of the 1+1-dimensional SU(3) lattice gauge theory is used to define an efficient mapping of SU(3) invariant degrees of freedom onto qubits. It is shown that the required number of qubits in the LSH basis is significantly reduced compared to its IRREP basis counterpart. While the non-Abelian Gauss laws of the SU(3) theory are automatically satisfied by the usage of LSH variables, the remnant constraints on the consistency of the flux numbers still exist. During time evolution, the noise can accumulate and take the state out of the sector of the Hilbert space where the constraint is satisfied. With this motivation, an oracle algorithm is constructed to be applied to the qubits for checking the local constraint at a given link. Costs in terms of qubit and gate number, and circuit depth, are found.