Quantum ratchet control —Harvesting on Landau-Zener transitions

¹  Department of Physics and Center for Computational Science and Engineering, National University of Singapore 117542, Republic of Singapore
²  Max-Planck-Institut für Physik Komplexer Systeme - Nöthnitzer Str. 38, 01187 Dresden, Germany, EU
³  NUS Graduate School for Integrative Sciences and Engineering - Singapore 117597, Republic of Singapore

Received: 9 April 2008
Accepted: 30 June 2008

Abstract

We control the current of a single-particle quantum ratchet by designing ramping schemes for experimentally accessible control parameters. We harvest on Landau-Zener transitions between Floquet states. Adiabatic and diabatic ramping allow to control the resulting directed transport. We find strong changes of the current in the adiabatic regime. Simple loops in control parameter space with alternating adiabatic and diabatic ramping are proposed. We obtain also current reversal. Full desymmetrization of the quantum ratchet increases the critical ramping speed which separates the adiabatic from the diabatic regime.