15,765 research outputs found
Bose-glass to Superfluid transition in the three-dimensional Bose-Hubbard Model
We present a Monte Carlo study of the Bose-glass to superfluid transition in
the three-dimensional Bose-Hubbard model. Simulations are performed on the
classical (3 + 1) dimensional link-current representation using the geometrical
worm algorithm. Finite-size scaling analysis (on lattices as large as
16x16x16x512 sites) of the superfluid stiffness and the compressibility is
consistent with a value of the dynamical critical exponent z = 3, in agreement
with existing scaling and renormalization group arguments that z = d. We find
also a value of for the correlation length exponent,
satisfying the relation . However, a detailed study of the
correlation functions, C(r, tau), at the quantum critical point are not
consistent with this value of z. We speculate that this discrepancy could be
due to the fact that the correlation functions have not reached their true
asymptotic behavior because of the relatively small spatial extent of the
lattices used in the present study.Comment: 9 pages, 8 figures, submitted to PR
Measurement induced entanglement and quantum computation with atoms in optical cavities
We propose a method to prepare entangled states and implement quantum
computation with atoms in optical cavities. The internal state of the atoms are
entangled by a measurement of the phase of light transmitted through the
cavity. By repeated measurements an entangled state is created with certainty,
and this entanglement can be used to implement gates on qubits which are stored
in different internal degrees of freedom of the atoms. This method, based on
measurement induced dynamics, has a higher fidelity than schemes making use of
controlled unitary dynamics.Comment: 4 pages including 2 figures. v2+3: minor change
Photon scattering by a three-level emitter in a one-dimensional waveguide
We discuss the scattering of photons from a three-level emitter in a
one-dimensional waveguide, where the transport is governed by the interference
of spontaneously emitted and directly transmitted waves. The scattering problem
is solved in closed form for different level structures. Several possible
applications are discussed: The state of the emitter can be switched
deterministically by Raman scattering, thus enabling applications in quantum
computing such as a single photon transistor. An array of emitters gives rise
to a photonic band gap structure, which can be tuned by a classical driving
laser. A disordered array leads to Anderson localization of photons, where the
localization length can again be controlled by an external driving.Comment: 17 pages, 8 figure
Hydrodynamics of a new concept of primary containment by energy absorption
Fluid dynamical analysis for idealized reactors system with spherical symmetry determines the effect which the destructive component of a nuclear accident produces on primary containment structures. Steel strands surrounding the reactor cavity in the biological shield exhibit plastic deformation to achieve the energy absorption
Suppression of Non-photonic Electrons from Enhancement of Charm Baryons in Heavy Ion Collisions
At intermediate transverse momentum (2 < p_T < 6 GeV/c), baryon production in
Au+Au collisions is enhanced compared to p+p collisions. Since charm baryon
decays produce electrons less frequently than charm meson decays, the
non-photonic electron spectrum is sensitive to the Lambda_c/D ratio. In this
report we study the dependence of the non-photonic electron spectrum on the
baryon-to-meson ratio for charm hadrons. As an example, we take the Lambda_c/D
ratio to have the same form as the Lambda/K^0_S ratio. In this case, even if
the total charm quark yield in Au+Au collisions scales with the number of
binary nucleon-nucleon collisions (N_bin), the electron spectrum at 2 < p_T < 5
GeV/c is suppressed relative to N_bin scaled p+p collisions by as much as 20%.Comment: Added STAR data to figure 1 and made slight text modifications (fixed
figure replacement
Quantum emitters coupled to surface plasmons of a nano-wire: A Green function approach
We investigate a system consisting of a single, as well as two emitters
strongly coupled to surface plasmon modes of a nano-wire using a Green function
approach. Explicit expressions are derived for the spontaneous decay rate into
the plasmon modes and for the atom-plasmon coupling as well as a
plasmon-mediated atom-atom coupling. Phenomena due to the presence of losses in
the metal are discussed. In case of two atoms, we observe Dicke sub- and
superradiance resulting from their plasmon-mediated interaction. Based on this
phenomenon, we propose a scheme for a deterministic two-qubit quantum gate. We
also discuss a possible realization of interesting many-body Hamiltonians, such
as the spin-boson model, using strong emitter-plasmon coupling.Comment: 12 pages, 16 figure
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