1,475 research outputs found
Preparation and detection of magnetic quantum phases in optical superlattices
We describe a novel approach to prepare, detect and characterize magnetic
quantum phases in ultra-cold spinor atoms loaded in optical superlattices. Our
technique makes use of singlet-triplet spin manipulations in an array of
isolated double well potentials in analogy to recently demonstrated quantum
control in semiconductor quantum dots. We also discuss the many-body
singlet-triplet spin dynamics arising from coherent coupling between nearest
neighbor double wells and derive an effective description for such system. We
use it to study the generation of complex magnetic states by adiabatic and
non-equilibrium dynamics.Comment: 5 pages, 2 Figures, reference adde
Decay of super-currents in condensates in optical lattices
In this paper we discuss decay of superfluid currents in boson lattice
systems due to quantum tunneling and thermal activation mechanisms. We derive
asymptotic expressions for the decay rate near the critical current in two
regimes, deep in the superfluid phase and close to the superfluid-Mott
insulator transition. The broadening of the transition at the critical current
due to these decay mechanisms is more pronounced at lower dimensions. We also
find that the crossover temperature below which quantum decay dominates is
experimentally accessible in most cases. Finally, we discuss the dynamics of
the current decay and point out the difference between low and high currents.Comment: Contribution to the special issue of Journal of Superconductivity in
honor of Michael Tinkham's 75th birthda
Variational optimization of tensor-network states with the honeycomb-lattice corner transfer matrix
We develop a method of variational optimization of the infinite projected
entangled pair states on the honeycomb lattice. The method is based on the
automatic differentiation of the honeycomb lattice corner transfer matrix
renormalization group. We apply the approach to the antiferromagnetic
Heisenberg spin-1/2 model on the honeycomb lattice. The developed formalism
gives quantitatively accurate results for the main physical observables and has
a necessary potential for further extensions
Superfluid-insulator transition in a moving system of interacting bosons
We analyze stability of superfluid currents in a system of strongly
interacting ultra-cold atoms in an optical lattice. We show that such a system
undergoes a dynamic, irreversible phase transition at a critical phase gradient
that depends on the interaction strength between atoms. At commensurate
filling, the phase boundary continuously interpolates between the classical
modulation instability of a weakly interacting condensate and the equilibrium
quantum phase transition into a Mott insulator state at which the critical
current vanishes. We argue that quantum fluctuations smear the transition
boundary in low dimensional systems. Finally we discuss the implications to
realistic experiments.Comment: updated refernces and introduction, minor correction
Storage of light in atomic vapor
We report an experiment in which a light pulse is decelerated and trapped in
a vapor of Rb atoms, stored for a controlled period of time, and then released
on demand. We accomplish this storage of light by dynamically reducing the
group velocity of the light pulse to zero, so that the coherent excitation of
the light is reversibly mapped into a collective Zeeman (spin) coherence of the
Rb vapor
Optical Superradiance from Nuclear Spin Environment of Single Photon Emitters
We show that superradiant optical emission can be observed from the polarized
nuclear spin ensemble surrounding a single photon emitter such as a single
quantum dot (QD) or Nitrogen-Vacancy (NV) center. The superradiant light is
emitted under optical pumping conditions and would be observable with realistic
experimental parameters.Comment: 4+ pages, 3 figures, considerably rewritten, conclusions unchanged,
accepted versio
Tracer-encapsulated pellet injector for plasma diagnostics
An injector for making solid hydrogen pellets around impurity cores has been developed for plasma transport study in large helical device. A technique has been employed for automatic loading carbon or polystyrene cores of 0.2 mm diameter from a gun magazine to a light-gas gun barrel. The injector is equipped with a cryocooler and is able to form a 3.2 mm long and 3 mm diameter cylindrical solid hydrogen pellet at 7 8 K with an impurity core in its center within 6 min and to inject it in the light-gas gun up to 1 km/s
Enhancement of Kerr nonlinearity via multi-photon coherence
We propose a new method of resonant enhancement of optical Kerr nonlinearity
using multi-level atomic coherence. The enhancement is accompanied by
suppression of the other linear and nonlinear susceptibility terms of the
medium. We show that the effect results in a modification of the nonlinear
Faraday rotation of light propagating in an Rb87 vapor cell by changing the
ellipticity of the light.Comment: 4 pages, 3 figures Submitted to Optics Letter
Threshold and linewidth of a mirrorless parametric oscillator
We analyze the above-threshold behavior of a mirrorless parametric oscillator
based on resonantly enhanced four wave mixing in a coherently driven dense
atomic vapor. It is shown that, in the ideal limit, an arbitrary small flux of
pump photons is sufficient to reach the oscillator threshold. We demonstrate
that due to the large group-velocity delays associated with coherent media, an
extremely narrow oscillator linewidth is possible, making a narrow-band source
of non-classical radiation feasible.Comment: revised version to appear in Phys.Rev.Lett., contains discussion on
threshold conditions and operation on few-photon leve
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