2,243 research outputs found
Synthetic Helical Liquids with Ultracold Atoms in Optical Lattices
We discuss a platform for the synthetic realization of key physical
properties of helical Tomonaga Luttinger liquids (HTLLs) with ultracold
fermionic atoms in one-dimensional optical lattices. The HTLL is a strongly
correlated metallic state where spin polarization and propagation direction of
the itinerant particles are locked to each other. We propose an unconventional
one-dimensional Fermi-Hubbard model which, at quarter filling, resembles the
HTLL in the long wavelength limit, as we demonstrate with a combination of
analytical (bosonization) and numerical (density matrix renormalization group)
methods. An experimentally feasible scheme is provided for the realization of
this model with ultracold fermionic atoms in optical lattices. Finally, we
discuss how the robustness of the HTLL against back-scattering and
imperfections, well known from its realization at the edge of two-dimensional
topological insulators, is reflected in the synthetic one-dimensional scenario
proposed here
Optical pumping of quantum dot nuclear spins
An all-optical scheme to polarize nuclear spins in a single quantum dot is
analyzed. The hyperfine interaction with randomly oriented nuclear spins
presents a fundamental limit for electron spin coherence in a quantum dot; by
cooling the nuclear spins, this decoherence mechanism could be suppressed. The
proposed scheme is inspired by laser cooling methods of atomic physics and
implements a "controlled Overhauser effect" in a zero-dimensional structure
Quantum feedback cooling of a single trapped ion in front of a mirror
We develop a theory of quantum feedback cooling of a single ion trapped in
front of a mirror. By monitoring the motional sidebands of the light emitted
into the mirror mode we infer the position of the ion, and act back with an
appropriate force to cool the ion. We derive a feedback master equation along
the lines of the quantum feedback theory developed by Wiseman and Milburn,
which provides us with cooling times and final temperatures as a function of
feedback gain and various system parameters.Comment: 15 pages, 11 Figure
Continuous Observation of Interference Fringes from Bose Condensates
We use continuous measurement theory to describe the evolution of two Bose
condensates in an interference experiment. It is shown how the system evolves
in a single run of the experiment into a state with a fixed relative phase,
while the total gauge symmetry remains unbroken. Thus, an interference pattern
is exhibited without violating atom number conservation.Comment: 4 pages, Postscrip
Fault-Tolerant Dissipative Preparation of Atomic Quantum Registers with Fermions
We propose a fault tolerant loading scheme to produce an array of fermions in
an optical lattice of the high fidelity required for applications in quantum
information processing and the modelling of strongly correlated systems. A cold
reservoir of Fermions plays a dual role as a source of atoms to be loaded into
the lattice via a Raman process and as a heat bath for sympathetic cooling of
lattice atoms. Atoms are initially transferred into an excited motional state
in each lattice site, and then decay to the motional ground state, creating
particle-hole pairs in the reservoir. Atoms transferred into the ground
motional level are no longer coupled back to the reservoir, and doubly occupied
sites in the motional ground state are prevented by Pauli blocking. This scheme
has strong conceptual connections with optical pumping, and can be extended to
load high-fidelity patterns of atoms.Comment: 12 pages, 7 figures, RevTex
Creation of a molecular condensate by dynamically melting a Mott-insulator
We propose creation of a molecular Bose-Einstein condensate (BEC) by loading
an atomic BEC into an optical lattice and driving it into a Mott insulator (MI)
with exactly two atoms per site. Molecules in a MI state are then created under
well defined conditions by photoassociation with essentially unit efficiency.
Finally, the MI is melted and a superfluid state of the molecules is created.
We study the dynamics of this process and photoassociation of tightly trapped
atoms.Comment: minor revisions, 5 pages, 3 figures, REVTEX4, accepted by PRL for
publicatio
Superconducting Vortex Lattices for Ultracold Atoms
We propose and analyze a nanoengineered vortex array in a thin-film type-II
superconductor as a magnetic lattice for ultracold atoms. This proposal
addresses several of the key questions in the development of atomic quantum
simulators. By trapping atoms close to the surface, tools of nanofabrication
and structuring of lattices on the scale of few tens of nanometers become
available with a corresponding benefit in energy scales and temperature
requirements. This can be combined with the possibility of magnetic single site
addressing and manipulation together with a favorable scaling of
superconducting surface-induced decoherence.Comment: Published Version. Manuscript: 5 pages, 3 figures. Supplementary
Information: 11 pages, 7 figure
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