abstract: Single atoms in optical lattices are a powerful resource to explore quantum interference phenomena. We will present our experimental approach to manipulate individual atoms in state-dependent optical lattices. A set of discrete operations allows us to process the quantum information, which is stored in the position and spin of the atoms. These operations can be assembled together as the basic building blocks of a richer quantum system, for instance, to design the interfering paths of a single atom interferometer in a fully digital fashion 1. Matter wave interference can be extended from a simple Mach-Zehnder-like geometry to structured multipath geometries, as is the case of a discrete quantum walk of several tens of steps. This opens the way to studying quantum transport phenomena as the so-called “electric quantum walks,” which allow us to reproduce in a stroboscopic fashion the behavior of a charged particle in a crystal in the presence of an external electric field 2,3. In a closely related vein, we have recently demonstrated a violation of Leggett-Garg inequality by measuring temporal correlations of quantum walks by means of ideal negative measurements. Detected violations up to 6 σ provide a rigorous test for the non-classicality of quantum motion of massive particles. Further-more, systems of walking atoms hold promise for carrying out future transport experiments with few quantum-correlated particles 4.
References: 1: A. Steffen, A. Alberti, W. Alt, N. Belmechri, S. Hild, M. Karski, A. Widera and D. Meschede, A digital atom interferometer with single particle control on a discretized spacetime geometry, PNAS 109, 9770 (2012) 2: M. Genske, W. Alt, A. Steffen, A. H. Werner, R. F. Werner, D. Meschede, A. Alberti, Electric quantum walks with individual atoms, Phys. Rev. Lett. 110, 190601 (2013) 3: C. Cedzich, T. Rybár, A. H. Werner, A. Alberti, M. Genske and R. F. Werner, Propagation of quantum walks in electric fields, Phys. Rev. Lett. 111, 160601 (2013) 4: A. Ahlbrecht, A. Alberti, D. Meschede, V. B. Scholz, A. H. Werner, R. F. Werner, Molecular binding in interacting quantum walks, New. J. Phys., 14 073050 (2012)