We propose a new system for implementing quantum logic gates: neutral atoms trapped in a very far-off-resonance optical lattice. Pairs of atoms are made to occupy the same well by varying the polarization of the trapping lasers, and then a near-resonant electric dipole is induced by an auxiliary laser. A controlled-NOT can be implemented by conditioning the target atomic resonance on a resolvable level shift induced by the control atom. Atoms interact only during logical operations, thereby suppressing decoherence.Comment: Revised version, To appear in Phys. Rev. Lett. Three separate postscript figure

We describe the design and implementation of a 2D optical lattice of double wells suitable for isolating and manipulating an array of individual pairs of atoms in an optical lattice. Atoms in the square lattice can be placed in a double well with any of their four nearest neighbors. The properties of the double well (the barrier height and relative energy offset of the paired sites) can be dynamically controlled. The topology of the lattice is phase stable against phase noise imparted by vibrational noise on mirrors. We demonstrate the dynamic control of the lattice by showing the coherent splitting of atoms from single wells into double wells and observing the resulting double-slit atom diffraction pattern. This lattice can be used to test controlled neutral atom motion among lattice sites and should allow for testing controlled two-qubit gates.Bose Einstein condensates (BEC) in optical lattices have proven to be an exciting and rich environment for studying many areas of physics, such as condensed matter physics, atomic physics, and quantum information processing (see for instance [1]). Optical lattices are very versatile because they allow dynamic control of many important experimental parameters. Dynamic control of the amplitude of the lattice has been widely used (e.g. [2,3,4,5]); recent experiments have used a state dependent lattice to dynamically control the geometry and transport of atoms in the lattice [6]. Recently there have been several proposals for using optical lattices to perform neutral atom quantum computation [7,8,9]. With optical lattices it should be possible to load single atoms into individual lattice sites with high fidelity [10], and then to isolate and manipulate pairs of atoms confined by the lattice in order to perform 2-qubit gates. Loading of single atoms into lattice sites or traps was demonstrated by [5,11,12,13,14], but to date no neutral atom based trap can isolate and control interactions between individual pairs of atoms. While previous experiments have demonstrated the clustered entanglement of many atoms confined by an optical lattice [15], the unique ability to isolate and control interactions between pairs of atoms would allow for entanglement between just the pair of atoms.In this paper we report on a double well optical lattice designed to isolate and control pairs of atoms. The lattice is constructed from two 2D lattices with different spatial periods, resulting in a 2D lattice whose unit cell contains two sites. Within the pair, the barrier height and relative depths of the two sites are controllable. Furthermore, the orientation of the unit cell can be changed, allowing each lattice site to be paired with any one if its four nearest neighbors. The double well lattice is phase stable in that its topology is not sensitive to phase noise from motion of the mirrors. This lattice, in combination with an independent 1D lattice in the third direction to provide 3D confinement, is ideal for testing many 2 qubit ideas, particularly quantum computation based on the concept of "...

Chaotic behaviour is ubiquitous and plays an important part in most fields of science. In classical physics, chaos is characterized by hypersensitivity of the time evolution of a system to initial conditions. Quantum mechanics does not permit a similar definition owing in part to the uncertainty principle, and in part to the Schrödinger equation, which preserves the overlap between quantum states. This fundamental disconnect poses a challenge to quantum-classical correspondence, and has motivated a long-standing search for quantum signatures of classical chaos. Here we present the experimental realization of a common paradigm for quantum chaos-the quantum kicked top- and the observation directly in quantum phase space of dynamics that have a chaotic classical counterpart. Our system is based on the combined electronic and nuclear spin of a single atom and is therefore deep in the quantum regime; nevertheless, we find good correspondence between the quantum dynamics and classical phase space structures. Because chaos is inherently a dynamical phenomenon, special significance attaches to dynamical signatures such as sensitivity to perturbation or the generation of entropy and entanglement, for which only indirect evidence has been available. We observe clear differences in the sensitivity to perturbation in chaotic versus regular, non-chaotic regimes, and present experimental evidence for dynamical entanglement as a signature of chaos.