659 research outputs found
Scaling the neutral atom Rydberg gate quantum computer by collective encoding in Holmium atoms
We discuss a method for scaling a neutral atom Rydberg gate quantum processor
to a large number of qubits. Limits are derived showing that the number of
qubits that can be directly connected by entangling gates with errors at the
level using long range Rydberg interactions between sites in an
optical lattice, without mechanical motion or swap chains, is about 500 in two
dimensions and 7500 in three dimensions. A scaling factor of 60 at a smaller
number of sites can be obtained using collective register encoding in the
hyperfine ground states of the rare earth atom Holmium. We present a detailed
analysis of operation of the 60 qubit register in Holmium. Combining a lattice
of multi-qubit ensembles with collective encoding results in a feasible design
for a 1000 qubit fully connected quantum processor.Comment: 6 figure
A Seriuos Academic Work
С.А. Кравченко «Социологический толковый англо-русский словарь». М.: МГИМО(У) МИД России, 2012. 690 с. (Серия «Энциклопедии и словари МГИМО(У)»)
Renormalization Group Theory for a Perturbed KdV Equation
We show that renormalization group(RG) theory can be used to give an analytic
description of the evolution of a perturbed KdV equation. The equations
describing the deformation of its shape as the effect of perturbation are RG
equations. The RG approach may be simpler than inverse scattering theory(IST)
and another approaches, because it dose not rely on any knowledge of IST and it
is very concise and easy to understand. To the best of our knowledge, this is
the first time that RG has been used in this way for the perturbed soliton
dynamics.Comment: 4 pages, no figure, revte
Formation of Nanoclusters and Nanopillars in Nonequilibrium Surface Growth for Catalysis Applications: Growth by Diffusional Transport of Matter in Solution Synthesis
Growth of nanoclusters and nanopillars is considered in a model of surface
deposition of building blocks (atoms) diffusionally transported from solution
to the forming surface structure. Processes of surface restructuring are also
accounted for in the model, which then yields morphologies of interest in
catalysis applications. Kinetic Monte Carlo numerical approach is utilized to
explore the emergence of FCC-symmetry surface features in Pt-type metal
nanostructures. Available results exemplify evaluation of the fraction of the
resulting active sites with desirable properties for catalysis, such as
(111)-like coordination, as well as suggest optimal growth regimes
Photon echoes generated by reversing magnetic field gradients in a rubidium vapour
We propose a photon echo quantum memory scheme using detuned Raman coupling
to long lived ground states. In contrast to previous 3-level schemes based on
controlled reversible inhomogeneous broadening that use sequences of
-pulses, the scheme does not require accurate control of the coupling
dynamics to the ground states. We present a proof of principle experimental
realization of our proposal using rubidium atoms in a warm vapour cell. The
Raman resonance line is broadened using a magnetic field that varies linearly
along the direction of light propagation. Inverting the magnetic field gradient
rephases the atomic dipoles and re-emits the light pulse in the forward
direction
Enhancement of the electric dipole moment of the electron in the YbF molecule
We calculate an effective electric field on the unpaired electron in the YbF
molecule. This field determines sensitivity of the molecular experiment to the
electric dipole moment of the electron. We use experimental value of the
spin-doubling constant to estimate the admixture of the configuration with the
hole in the 4f-shell of Ytterbium to the ground state of the molecule. This
admixture reduces the field by 7%. Our value for the effictive field is 5.1
a.u. = 2.5 10^{10} V/cm.Comment: 5 pages, LATEX, uses revtex.st
Three- and Four-Body Scattering Calculations including the Coulomb Force
The method of screening and renormalization for including the Coulomb
interaction in the framework of momentum-space integral equations is applied to
the three- and four-body nuclear reactions. The Coulomb effect on the
observables and the ability of the present nuclear potential models to describe
the experimental data is discussed.Comment: Proceedings of the Critical Stability workshop, Erice, Sicily,
October 2008, to be published in Few-Body System
Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms
Fermionic alkaline-earth atoms have unique properties that make them
attractive candidates for the realization of novel atomic clocks and degenerate
quantum gases. At the same time, they are attracting considerable theoretical
attention in the context of quantum information processing. Here we demonstrate
that when such atoms are loaded in optical lattices, they can be used as
quantum simulators of unique many-body phenomena. In particular, we show that
the decoupling of the nuclear spin from the electronic angular momentum can be
used to implement many-body systems with an unprecedented degree of symmetry,
characterized by the SU(N) group with N as large as 10. Moreover, the interplay
of the nuclear spin with the electronic degree of freedom provided by a stable
optically excited state allows for the study of spin-orbital physics. Such
systems may provide valuable insights into strongly correlated physics of
transition metal oxides, heavy fermion materials, and spin liquid phases.Comment: 15 pages, 10 figures. V2: extended experimental accessibility and
Kondo sections in the main text (including new Fig. 5b) and in the Methods;
reorganized other parts; added reference
Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System
It is argued that ultracold quantum degenerate gas of ytterbium Yb
atoms having nuclear spin exhibits an enlarged SU symmetry.
Within the Landau Fermi liquid theory, stability criteria against Fermi liquid
(Pomeranchuk) instabilities in the spin channel are considered. Focusing on the
SU generalizations of ferromagnetism, it is shown within mean-field
theory that the transition from the paramagnet to the itinerant ferromagnet is
generically first order. On symmetry grounds, general SU itinerant
ferromagnetic ground states and their topological excitations are also
discussed. These SU ferromagnets can become stable by increasing the
scattering length using optical methods or in an optical lattice. However, in
an optical lattice at current experimental temperatures, Mott states with
different filling are expected to coexist in the same trap, as obtained from a
calculation based on the SU Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6)
symmetry-breaking patterns; v3: added further discussion on the order of the
transition. Added Reference
Dipolar collisions of polar molecules in the quantum regime
Ultracold polar molecules offer the possibility of exploring quantum gases
with interparticle interactions that are strong, long-range, and spatially
anisotropic. This is in stark contrast to the dilute gases of ultracold atoms,
which have isotropic and extremely short-range, or "contact", interactions. The
large electric dipole moment of polar molecules can be tuned with an external
electric field; this provides unique opportunities such as control of ultracold
chemical reactions, quantum information processing, and the realization of
novel quantum many-body systems. In spite of intense experimental efforts aimed
at observing the influence of dipoles on ultracold molecules, only recently
have sufficiently high densities been achieved. Here, we report the observation
of dipolar collisions in an ultracold molecular gas prepared close to quantum
degeneracy. For modest values of an applied electric field, we observe a
dramatic increase in the loss rate of fermionic KRb molecules due to ultrcold
chemical reactions. We find that the loss rate has a steep power-law dependence
on the induced electric dipole moment, and we show that this dependence can be
understood with a relatively simple model based on quantum threshold laws for
scattering of fermionic polar molecules. We directly observe the spatial
anisotropy of the dipolar interaction as manifested in measurements of the
thermodynamics of the dipolar gas. These results demonstrate how the long-range
dipolar interaction can be used for electric-field control of chemical reaction
rates in an ultracold polar molecule gas. The large loss rates in an applied
electric field suggest that creating a long-lived ensemble of ultracold polar
molecules may require confinement in a two-dimensional trap geometry to
suppress the influence of the attractive dipolar interactions
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