Coherent transport of single atoms in optical lattices

We describe a technique for transferring a two-level atom between two adjacent potential wells of an optical lattice, using pairs of pump and Stokes pulses, each resonantly coupling the same pair of internal atomic states to form a Raman transition. Starting from a vibrational eigenstate of one well the atom slowly moves under the action of the pulse pair, to the vibrational eigenstate with the same quantum number in the neighboring well. The transfer takes place in two stages: A conventional stimulated Raman adiabatic passage (STIRAP) technique, in which Stokes precedes pump pulse, is followed by a pulse sequence where pump precedes Stokes and with an inverted sign of the Stokes envelope. In the first step the atom is accelerated toward the adjacent well and in the second step decelerated to the initial vibrational energy. The STIRAP technique avoids the introduction of stochastic motion caused by spontaneous emission from the excited internal atomic state