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Engineering Coherences at Single-Atom Level

Andrea Alberti, Universität Bonn

(Session 3 : Friday from 11:45am-12:15pm)

Abstract. We report on our capabilities to coherently control individual neutral Cs atoms in a 1D optical lattice with single site resolution [1,2]. By controlling the atoms through spin-dependent optical potentials we are able to entangle their internal and external degrees of freedom, allowing us to demonstrate 1D quantum walks in real space. Multi-path matter wave interference results in characteristic patterns of coherently delocalized atoms over many lattice sites [3]. In addition, microwave control of atomic motion is used to prepare atoms in predefined motional quantum states, e.g. in the vibrational ground state [4]. Presently we are exploring single-atom interferometry using spatially delocalized atoms in a Mach-Zehnder-like geometry. The atomic wave packets accumulate a relative phase at their respective positions from potential differences, making it a microscopic quantum detector of forces, such as magnetic field gradients or accelerations. Spatial separations over more than 20 sites still yields usable coherent phase evolution. These results lay the basis for interferometric detection of collisional phases and two-atom entanglement generation. [1] M. Karski et al., Imprinting Patterns of Neutral Atoms in an Optical Lattice using Magnetic Resonance Techniques, New J. Phys. 12, 065027 (2010) [2] M. Karski et al., Nearest-Neighbor Detection of Atoms in a 1D Optical Lattice by Fluorescence Imaging, Phys. Rev. Lett. 102, 053001 (2009) [3] M. Karski et al., Quantum Walk in Position Space with Single Optically Trapped Atoms, Science 325, 174 (2009) [4] L. Förster et al., Microwave Control of Atomic Motion in Optical Lattices, Phys. Rev. Lett. 103, 233001 (2009)