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We experimentally demonstrate novel structures for the realization of registers of atomic qubits: We trap neutral atoms in one- and two-dimensional arrays of far-detuned dipole traps obtained by focusing a red-detuned laser beam with a microfabricated array of microlenses. We are able to selectively address individual trap sites due to their large lateral separation of 125 microm. We initialize and read out different internal states for the individual sites. We also create two interleaved sets of trap arrays with adjustable separation, as required for many proposed implementations of quantum gate operations.

We experimentally demonstrate and systematically study the stimulated revival (echo) of motional wave packet oscillations. For this purpose, we prepare wave packets in an optical lattice by non-adiabatically shifting the potential and stimulate their reoccurence by a second shift after a variable time delay. This technique, analogous to spin echoes, enables one even in the presence of strong dephasing to determine the coherence time of the wave packets. We find that for strongly bound atoms it is comparable to the cooling time and much longer than the inverse of the photon scattering rate.32.80. Pj, 42.50.Vk The process of decoherence, i.e. the collapse of superposition states due to the dissipative interaction with their environment is one of the basic concepts for our understanding of the connection between classical and quantum physics. In order to study the effect of decoherence unambiguously, one has to be able to distinguish it from other, non-dissipative effects. The macroscopic (i.e. ensemble-or time-averaged) response of a quantum system prepared in a superposition state typically decays not only due to the loss of coherence (homogeneous decay) but also due to dephasing resulting from local variations in the evolution of the quantum system (inhomogeneous decay). In many cases decoherence cannot be studied directly because the inhomogeneous decay is by far the dominating process.This limitation has been overcome in a famous series of experiments by introducing the techniques of spin echo for nuclear magnetic resonance (NMR) and photon echo for optical resonance, respectively [1][2][3]. These techniques are based on the observation that inhomogeneous decay due to dephasing is a reversible process. Thus, by appropriately modifying superposition states at a time ∆t after their preparation, the dephasing can be partially or fully reversed and a stimulated macroscopic response (echo) is induced at 2∆t. This effect enables one to measure the coherence time even in the presence of strong dephasing. We have, for the first time, applied this method to the investigation of the decoherence of motional wave packets of trapped atoms (Fig. 1). The method can be used independent of the specific experimental realization of the confining potential (e.g. a single dipole potential, periodic dipole potentials, magnetic trapping potentials, inhomogeneous arrays of atom traps, etc.).The specific system investigated here consists of motional wave packets of neutral atoms in a one-dimensional optical lattice. Optical lattices are periodic dipole potentials for atoms created by the interference of multiple laser beams [4]. Atoms can be trapped and cooled at the potential minima (mean position spread z rms =λ/18[5]). In optical lattices symmetrically and asymmetrically oscillating motional wave packets can be induced by nonadiabatically changing the lattice potential [6][7][8][9][10][11]. Quantum mechanically, the original atomic wave function is projected onto a coherent superposition of the eigenstates of the new potential a...

We have devised an all-optical setup for the generation of two phase-locked laser fields with a frequency difference of 3 GHz using only standard optics and two acousto-optical frequency shifters, that are operated at 253 MHz in sixtupel pass. The spectral width of the beat frequency is measured to be 300 Hz (full width at half maximum) limited by the resolution bandwidth of the spectrum analyzer. We routinely obtain an overall efficiency of more than 15% and demonstrate that the frequency shifted light can be further amplified by injecting it into additional “slave” lasers. This setup provides a low-cost alternative over conventional methods to generate laser fields with difference frequencies in the GHz domain, as for example, used in laser spectroscopy, laser cooling and trapping, and coherent manipulation of atomic quantum states.

We introduce a new direction in the ®eld of atom optics, atom interferometry, and neutral-atom quantum information processing. It is based on the use of microfabricated optical elements. With these elements versatile and integrated atom optical devices can be created in a compact fashion. This approach opens the possibility to scale, parallelize, and miniaturize atom optics for new investigations in fundamental research and application. It will lead to new, compact sources of ultracold atoms, compact sensors based on matter wave interference and new approaches towards quantum computing with neutral atoms. The exploitation of the unique features of the quantum mechanical behavior of matter waves and the capabilities of powerful state-of-the-art micro-and nanofabrication techniques lend this approach a special attraction.