135 research outputs found
Reply to "Comment on 'Stimulated Raman adiabatic passage from an atomic to a molecular Bose-Einstein condensate'"
In the Comment by M. Mackie \textit{et al.} [arXiv: physics/0212111 v.4], the
authors suggest that the molecular conversion efficiency in atom-molecule
STIRAP can be improved by lowering the initial atomic density, which in turn
requires longer pulse durations to maintain adiabaticity. Apart from the fact
that the mean-field approximation becomes questionable at low densities, we
point out that a low-density strategy with longer pulses has several problems.
It generally requires higher pulse energies, and increases radiative losses. We
also show that even within the approximations used in the Comment, their
example leads to no efficiency improvement compared to our high-density case.
In a more careful analysis including radiative losses neglected in the Comment,
the proposed strategy gives almost no conversion owing to the longer pulse
durations required.Comment: Accepted for publication in Phys. Rev.
Polyatomic Molecules Formed with a Rydberg Atom in an Ultracold Environment
We investigate properties of ultralong-range polyatomic molecules formed with
a Rb Rydberg atom and several ground-state atoms whose distance from the
Rydberg atom is of the order of n^2a_0, where n is the principle quantum number
of the Rydberg electron. In particular, we put emphasis on the splitting of the
energy levels, and elucidate the nature of the splitting via the construction
of symmetry-adapted orbitals.Comment: 2 columns, 7 pages, 7 figures. Final verso
Quantum instabilities in the system of identical bosons
The quantum instability of the mean-field theory for identical bosons is
shown to be described by an appropriate Bogoliubov transformation. A connection
between the quantum and classical linear stability theories is indicated. It is
argued that the instability rate in a system of identical bosons must be
strongly affected by the nonlinear terms (interactions). In the case of the
repulsive interactions or strong attractive interactions the instability rate
is suppressed. On the other hand, a weak attraction significantly enhances the
instability rate. The results can have applications in the field of
Bose-Einstein condensates of dilute quantum gases.Comment: 12 pages. 2 figures. To appear in Physics Letters
Михайло Грушевський в історії України (Mikhailo Hrushevs’kyi in history of Ukraine)
У статті характеризується роль Михайла Грушевського у розвитку історичної науки
та політичному житті України. Наголошується на внеску вченого у розбудову українських
наукових інституцій: Наукового товариства ім. Шевченка, Академії наук тощо (The article characterized the role of Mykhailo Hrushevsky in the development of historical
scholarship and political life of Ukraine. Emphasis is on scientific contributions to the development
of Ukrainian research institutions: Shevchenko Scientific Society , Academy of Sciences of others
Quantum computations with atoms in optical lattices: marker qubits and molecular interactions
We develop a scheme for quantum computation with neutral atoms, based on the
concept of "marker" atoms, i.e., auxiliary atoms that can be efficiently
transported in state-independent periodic external traps to operate quantum
gates between physically distant qubits. This allows for relaxing a number of
experimental constraints for quantum computation with neutral atoms in
microscopic potential, including single-atom laser addressability. We discuss
the advantages of this approach in a concrete physical scenario involving
molecular interactions.Comment: 15 pages, 14 figure
Quantum Dynamics of Atom-molecule BECs in a Double-Well Potential
We investigate the dynamics of two-component Bose-Josephson junction composed
of atom-molecule BECs. Within the semiclassical approximation, the multi-degree
of freedom of this system permits chaotic dynamics, which does not occur in
single-component Bose-Josephson junctions. By investigating the level
statistics of the energy spectra using the exact diagonalization method, we
evaluate whether the dynamics of the system is periodic or non-periodic within
the semiclassical approximation. Additionally, we compare the semiclassical and
full-quantum dynamics.Comment: to appear in JLTP - QFS 200
Boson-like quantum dynamics of association in ultracold Fermi gases
We study the collective association dynamics of a cold Fermi gas of
atoms in atomic modes into a single molecular bosonic mode. The many-body
fermionic problem for amplitudes is effectively reduced to a dynamical
system of amplitudes, making the solution no more complex than
the solution of a two-mode Bose-Einstein condensate and allowing realistic
calculations with up to particles. The many-body dynamics is shown to be
formally similar to the dynamics of the bosonic system under the mapping of
boson particles to fermion holes, producing collective enhancement effects due
to many-particle constructive interference. Dissociation rates are shown to
enhance as the number of particles whereas association rates are enhanced as
the number of holes, leading to boson-like collective behavior.Comment: 5 pages, 2 figures, critical typo in Eq. (13) correcte
Controlling two-species Mott-insulator phses in an optical lattice to form an array of dipolar molecules
We consider the transfer of a two-species Bose-Einstein condensate into an
optical lattice with a density such that that a Mott-insulator state with one
atom per species per lattice site is obtained in the deep lattice regime.
Depending on collision parameters the result could be either a `mixed' or a
`separated' Mott-insulator phase. Such a `mixed' two-species insulator could
then be photo-associated into an array of dipolar molecules suitable for
quantum computation or the formation of a dipolar molecular condensate. For the
case of a Rb-K two-species BEC, however, the large inter-species
scattering length makes obtaining the desired `mixed' Mott insulator phase
difficult. To overcome this difficulty we investigate the effect of varying the
lattice frequency on the mean-field interaction and find a favorable parameter
regime under which a lattice of dipolar molecules could be generated
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