Quantum annealing of a frustrated magnet

TL;DR

This study demonstrates quantum annealing in a frustrated magnet, showing how tiny transverse fields can induce rapid convergence to low-energy states through quantum tunnelling, with implications for quantum computing.

Contribution

First single-crystal observation of quantum annealing phenomena in a frustrated magnet driven by tiny transverse fields, linking experimental results with many-body simulations.

Findings

Quantum annealing observed in $ ext{α}$-CoV$_2$O$_6$

Tiny transverse field induces rapid state convergence

Simulation results align qualitatively with experiments

Abstract

Quantum annealing, which involves quantum tunnelling among possible solutions, has state-of-the-art applications not only in quickly finding the lowest-energy configuration of a complex system, but also in quantum computing. Here we report a single-crystal study of the frustrated magnet $\alpha$-CoV$_2$O$_6$, consisting of a triangular arrangement of ferromagnetic Ising spin chains without evident structural disorder. We observe quantum annealing phenomena resulting from time-reversal symmetry breaking in a tiny transverse field. Below $\sim$ 1 K, the system exhibits no indication of approaching the lowest-energy state for at least 15 hours in zero transverse field, but quickly converges towards that configuration with a nearly temperature-independent relaxation time of $\sim$ 10 seconds in a transverse field of $\sim$ 3.5 mK. Our many-body simulations show qualitative agreement with the experimental results, and suggest that a tiny transverse field can profoundly enhance quantum spin fluctuations, triggering rapid quantum annealing process from topological metastable Kosterlitz-Thouless phases, at low temperatures.