Marco Anderlini

Lattice of double wells for manipulating pairs of cold atoms

We describe the design and implementation of a two-dimensional 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.

Sublattice addressing and spin-dependent motion of atoms in a double-well lattice.

We load atoms into every site of an optical lattice and selectively spin flip atoms in a sublattice consisting of every other site. These selected atoms are separated from their unselected neighbors by less than an optical wavelength. We also show spin-dependent transport, where atomic wave packets are coherently separated into adjacent sites according to their internal state. These tools should be useful for quantum information processing and quantum simulation of lattice models with neutral atoms.

Preparing and probing atomic number states with an atom interferometer.

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state.

Controlled atom dynamics in a double-well optical lattice

We report on the experimental demonstration of dynamic control of the motional state of atoms in a 2D double-well optical lattice. First we describe experiments in which the atomic distributions obtained by loading Bose–Einstein condensates of rubidium atoms in the lattice are dynamically split by transforming a 2D lattice with period λ into a 2D lattice with period λ/2, and we show how this procedure allows for the study of the coherence and interaction properties of the system. Then we show how we can efficiently adiabatically transfer the population between adjacent sites of the lattice, as well as between different energy bands, by using dynamic modifications of the potential.

Optimal control of atom transport for quantum gates in optical lattices

By means of optimal control techniques we model and optimize the manipulation of the external quantum state center-of-mass motion of atoms trapped in adjustable optical potentials. We consider in detail the cases of both noninteracting and interacting atoms moving between neighboring sites in a lattice of a double-well optical potentials. Such a lattice can perform interaction-mediated entanglement of atom pairs and can realize two-qubit quantum gates. The optimized control sequences for the optical potential allow transport faster and with significantly larger fidelity than is possible with processes based on adiabatic transport.

Thermalization in mixtures of ultracold gases

Starting from a set of coupled Boltzmann equations, we investigate the thermalization of a two-species cold atomic gas confined either in a box or in an isotropic harmonic trap. We show that the thermalization times, by contrast to the collision rate, depend on the interferences between scattering partial waves. The dynamics of thermalization in a harmonic trap is also strongly dependent upon the ratio between the collision rate and the trap frequencies.

Preparation and measurement of few-atom number states with a double-well atom interferometer

We use a double-well optical lattice as an atom interferometer to load and measure atomic number-squeezed states with N = 1 or 2 and Poissonian states with ¿N¿ ¿ 1 into the lattice ground state.

Site-selectivity and spin exchange in a double-well optical lattice

We have demonstrated site-selective radio frequency addressing of atoms with subwavelength resolution and a spin-exchange mechanism for a square root of swap gate in a spindependent double-well optical lattice.

Determination of the scattering length of the a {sup 3}{sigma}{sup +} potential of {sup 87}RbCs

We have determined the scattering length of the a {sup 3}{sigma}{sup +} potential of {sup 87}RbCs based on experimental observations from the literature and the known value for the long-range dispersion coefficient. Our analysis uses quantum defect theory and analytical solutions of the Schroedinger equation for a van der Waals potential. We find that the scattering length is either 700{sub -300}{sup +700}a{sub 0} or (176{+-}2)a{sub 0} with more confidence associated with the first value, where a{sub 0}=0.052 92 nm is the Bohr radius. An independent value of the van der Waals coefficient could not be determined and the best theoretically determined C{sub 6} value was used.

A Double Well Lattice for Dynamically Manipulating Pairs of Cold Atoms

We describe the design and implementation of a double-well optical lattice suitable for isolating and manipulating individual pairs of atoms. This lattice will be used to test controlled atom motion and controlled two-qubit gates.