Evidence for a Quantum-to-Classical Transition in a Pair of Coupled Quantum Rotors

TL;DR

This paper experimentally demonstrates how a pair of coupled quantum rotors can exhibit a transition from quantum to classical behavior, showing classical diffusion emerging from quantum dynamics in a controlled atomic system.

Contribution

The study provides the first experimental realization of coupled quantum rotors demonstrating a quantum-to-classical transition, confirming long-standing theoretical predictions.

Findings

Breakdown of dynamical localization in coupled rotors

Emergence of classical diffusion in quantum system

Distinct momentum transport behavior compared to single rotor

Abstract

The understanding of how classical dynamics can emerge in closed quantum systems is a problem of fundamental importance. Remarkably, while classical behavior usually arises from coupling to thermal fluctuations or random spectral noise, it may also be an innate property of certain isolated, periodically driven quantum systems. Here, we experimentally realize the simplest such system, consisting of two coupled, kicked quantum rotors, by subjecting a coherent atomic matter wave to two periodically pulsed, incommensurate optical lattices. Momentum transport in this system is found to be radically different from that in a single kicked rotor, with a breakdown of dynamical localization and the emergence of classical diffusion. Our observation, which confirms a long-standing prediction for many-dimensional quantum-chaotic systems, sheds new light on the quantum-classical correspondence.