Scientific Results

Quantum diffusion with disorder, noise and interaction

Year: 2013

Authors: D’Errico C., Moratti M., Lucioni E., Tanzi L., Deissler B., Inguscio M., Modugno G, Plenio M. B., Caruso F.

Autors Affiliation: LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, and INO-CNR, I-50019 Sesto Fiorentino, Italy; Institut für Quantenmaterie, Universität Ulm, Albert-Einstein-Allee 45, D-89069 Ulm, Germany; QSTAR, Largo Enrico Fermi 2, I-50125 Firenze, Italy; Institut für Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany

Abstract: Disorder, noise and interaction play a crucial role in the transport properties of real systems, but they are typically hard to control and study, both theoretically and experimentally, especially in the quantum case. Here, we explore a paradigmatic problem, the diffusion of a wavepacket, by employing ultra-cold atoms in a quasi-periodic lattice with controlled noise and tunable interaction. The presence of quasi-disorder leads to Anderson localization, while both interaction and noise tend to suppress localization and restore transport, although with completely different mechanisms. When only noise or interaction is present, we observe a diffusion dynamics that can be explained by existing microscopic models. When noise and interaction are combined, we observe instead a complex anomalous diffusion. By combining experimental measurements with numerical simulations, we show that such anomalous behavior can be modeled with a generalized diffusion equation in which the noise-and interaction-induced diffusions enter in an additive manner. Our study reveals also a more complex interplay between the two diffusion mechanisms in the regimes of strong interaction or narrowband noise.


Volume: 15      Pages from: 045007  to: 045007

More Information: We thank Lorenzo Gori for valuable contributions to the experiment and Shmuel Fishman and Michele Modugno for fruitful discussions. This work was supported by the ERC projects QUPOL and DISQUA, the EU projects Q-ESSENCE and AQUTE, the EU Marie-Curie Programme, MIUR (FIRB-RBFR10M3SB and PRIN-2009FBKLNN) and the Alexander von Humboldt Foundation. BD acknowledges support from the Carl-Zeiss-Stiftung. The QSTAR is the MPQ, LENS, IIT, UniFi Joint Center for Quantum Science and Technology in Arcetri. FC acknowledges QSTAR as well as the Imperial College High Performance Computing Service for computational resources.
KeyWords: Anderson localization; Anomalous behavior; Anomalous diffusion; Different mechanisms; Diffusion mechanisms; Experimental measurements; Generalized diffusion equation; Quasi-periodic lattices, Partial differential equations; Transport properties, Diffusion
DOI: 10.1088/1367-2630/15/4/045007

Citations: 37
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