Quantum simulations of localization effects with dipolar interactions

TL;DR

This paper investigates how disorder and perturbations in dipolar interactions cause localization of information spreading in quantum systems, using nuclear spin-based simulations to observe phenomena similar to Anderson localization.

Contribution

It demonstrates that strong disorder in dipolar-coupled quantum systems leads to localization, extending previous work by analyzing disordered Hamiltonians with 1/r^3 interactions.

Findings

Localization occurs with large disorder, halting coherence length expansion.

Dipolar interactions cause spreading that is limited by perturbations.

System exhibits behavior similar to Anderson localization.

Abstract

Quantum information processing often uses systems with dipolar interactions. We use a nuclear spin-based quantum simulator, to study the spreading of information in such a dipolar-coupled system and how perturbations to the dipolar couplings limit the spreading, leading to localization. In [Phys. Rev. Lett. 104, 230403 (2010)], we found that the system reaches a dynamic equilibrium size, which decreases with the square of the perturbation strength. Here, we study the impact of a disordered Hamiltonian with dipolar 1/r^3 interactions. We show that the expansion of the coherence length of the cluster size of the spins becomes frozen in the presence of large disorder, reminiscent of Anderson localization of non-interacting waves in a disordered potential.