Entangling Dipole-Dipole Interactions and Quantum Logic in Optical Lattices

Abstract

We study a means of creating multiparticle entanglement of neutral atoms using pairwise controlled dipole-dipole interactions in a three dimensional optical lattice. For tightly trapped atoms the dipolar interaction energy can be much larger than the photon scattering rate, and substantial coherent evolution of the two-atom state can be achieved before decoherence occurs. Excitation of the dipoles can be made conditional on the atomic states, allowing for deterministic generation of entanglement. We derive selection rules and a figure-of-merit for the dipole-dipole interaction matrix elements, for alkali atoms with hyperfine structure and trapped in well localized center of mass states. Different protocols are presented for implementing two-qubits quantum logic gates such as the controlled-phase and swap gate. We analyze the fidelity of our gate designs, imperfect due to decoherence from cooperative spontaneous emission and coherent couplings outside the logical basis. Outlines for extending our model to include the full molecular interactions potentials are discussed.