Article

Coherent control of atomic transport in spinor optical lattices

Physical Review A (Impact Factor: 2.99). 05/2009; 81(2). DOI: 10.1103/PhysRevA.81.023403
Source: arXiv

ABSTRACT Coherent transport of atoms trapped in an optical lattice can be controlled
by microwave-induced spin flips that correlate with site-to-site hopping. We
study the controllability of homogeneous one-dimensional systems of
noninteracting atoms in the absence of site addressability. Given these
restrictions, we construct a deterministic protocol to map an initially
localized Wannier state to a wave packet that that is coherently distributed
over n sites. This is extended to analytic solutions for arbitrary unitary maps
given homogenous systems and in the presence of time-dependent uniform forces.
Such control is important for applications in quantum information processing
such as quantum computing and quantum simulations of condensed matter
phenomena.

0 Bookmarks
 · 
83 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Quantum optimal control has enjoyed wide success for a variety of theoretical and experimental objectives. These favorable results have been attributed to advantageous properties of the corresponding control landscapes, which are free from local optima if three conditions are met: (1) the quantum system is controllable, (2) the Jacobian of the map from the control field to the evolution operator is full rank, and (3) the control field is not constrained. This paper explores how gradient searches for globally optimal control fields are affected by deviations from assumption (2). In some quantum control problems, so-called singular critical points, at which the Jacobian is rank-deficient, may exist on the landscape. Using optimal control simulations, we show that search failure is only observed when a singular critical point is also a second-order trap, which occurs if the control problem meets additional conditions involving the system Hamiltonian and/or the control objective. All known second-order traps occur at constant control fields, and we also show that they only affect searches that originate very close to them. As a result, even when such traps exist on the control landscape, they are unlikely to affect well-designed gradient optimizations under realistic searching conditions.
    Physical Review A 05/2014; 90(1). DOI:10.1103/PhysRevA.90.013404 · 2.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: By applying complementary analytic and numerical methods, we investigate the dynamics of spin-$1/2$ XXZ models with variable-range interactions in arbitrary dimensions. The dynamics we consider is initiated from uncorrelated states that are easily prepared in experiments, and can be equivalently viewed as either Ramsey spectroscopy or a quantum quench. Our primary focus is the dynamical emergence of correlations and entanglement in these far-from-equilibrium interacting quantum systems: we characterize these correlations by the entanglement entropy, concurrence, and squeezing, which are inequivalent measures of entanglement corresponding to different quantum resources. In one spatial dimension, we show that the time evolution of correlation functions manifests a non-perturbative dynamic singularity. This singularity is characterized by a universal power-law exponent that is insensitive to small perturbations. Explicit realizations of these models in current experiments using polar molecules, trapped ions, Rydberg atoms, magnetic atoms, and alkaline-earth and alkali atoms in optical lattices, along with the relative merits and limitations of these different systems, are discussed.
    Physical Review A 12/2014; 90(6):063622. DOI:10.1103/PhysRevA.90.063622 · 2.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spin-dependent optical potentials allow us to use microwave radiation to manipulate the motional state of trapped neutral atoms (F\"orster et al. 2009 Phys. Rev. Lett. 103, 233001). Here, we discuss this method in greater detail, comparing it to the widely-employed Raman sideband coupling method. We provide a simplified model for sideband cooling in a spin-dependent potential, and we discuss it in terms of the generalized Lamb-Dicke parameter. Using a master equation formalism, we present a quantitative analysis of the cooling performance for our experiment, which can be generalized to other experimental settings. We additionally use microwave sideband transitions to engineer motional Fock states and coherent states, and we devise a technique for measuring the population distribution of the prepared states.
    Journal of Physics B Atomic Molecular and Optical Physics 02/2013; 46(10). DOI:10.1088/0953-4075/46/10/104006 · 1.92 Impact Factor

Full-text (2 Sources)

Download
21 Downloads
Available from
Jun 23, 2014