Enhanced Quantum behavior on frustrated Ising model: Quantum Approximate Optimization Algorithm study

TL;DR

This paper explores quantum effects in a frustrated Ising model using QAOA, revealing how quantum fluctuations become prominent near phase transitions, and introduces a metric to quantify these effects.

Contribution

The study introduces a new metric to evaluate quantum effects in frustrated Ising models and applies QAOA to distinguish classical from quantum regimes.

Findings

Quantum fluctuations are more prominent near the phase transition.

QAOA rarely captures first excited states in weakly frustrated regions.

Excited states are more frequently observed near the quantum phase transition.

Abstract

We investigated the quantum effects of a frustrated Ising model on a two-dimensional square lattice using the Quantum Approximate Optimization Algorithm (QAOA). While strong spin frustration is known to induce quantum fluctuations at low temperatures, previous classical approaches restricted to binary (up or down) spin configurations have been insufficient to fully capture the quantum contributions of frustration. In this study, we introduced a quantitative metric to evaluate the quantum effects arising from frustration and employed QAOA to differentiate between classical and quantum regimes. Notably, we found that in the weakly frustrated region, QAOA measurements rarely capture first excited states, as they are energetically well separated from the ground state. In contrast, near the quantum phase transition point, excited states appear more frequently in QAOA measurements, highlighting the increased role of quantum fluctuations.