3,623 research outputs found
Studies of the black swamp snake, Seminatrix pygaea (Cope), with descriptions of two new subspecies
http://deepblue.lib.umich.edu/bitstream/2027.42/56321/1/MP076.pd
Hybrid Quantum System of a Nanofiber Mode Coupled to Two Chains of Optically Trapped Atoms
A tapered optical nanofiber simultaneously used to trap and optically
interface of cold atoms through evanescent fields constitutes a new and well
controllable hybrid quantum system. The atoms are trapped in two parallel 1D
optical lattices generated by suitable far blue and red detuned evanescent
field modes very close to opposite sides of the nanofiber surface. Collective
electronic excitations (excitons) of each of the optical lattices are
resonantly coupled to the second lattice forming symmetric and antisymmetric
common excitons. In contrast to the inverse cube dependence of the individual
atomic dipole-dipole interaction, we analytically find an exponentially
decaying coupling strength with distance between the lattices. The resulting
symmetric (bright) excitons strongly interact with the resonant nanofiber
photons to form fiber polaritons, which can be observed through linear optical
spectra. For large enough wave vectors the polariton decay rate to free space
is strongly reduced, which should render this system ideal for the realization
of long range quantum communication between atomic ensembles.Comment: 9 pages, 9 figure
Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber
Trapping and optically interfacing laser-cooled neutral atoms is an essential
requirement for their use in advanced quantum technologies. Here we
simultaneously realize both of these tasks with cesium atoms interacting with a
multi-color evanescent field surrounding an optical nanofiber. The atoms are
localized in a one-dimensional optical lattice about 200 nm above the nanofiber
surface and can be efficiently interrogated with a resonant light field sent
through the nanofiber. Our technique opens the route towards the direct
integration of laser-cooled atomic ensembles within fiber networks, an
important prerequisite for large scale quantum communication schemes. Moreover,
it is ideally suited to the realization of hybrid quantum systems that combine
atoms with, e.g., solid state quantum devices
Entangled Light in Moving Frames
We calculate the entanglement between a pair of polarization-entangled photon
beams as a function of the reference frame, in a fully relativistic framework.
We find the transformation law for helicity basis states and show that, while
it is frequency independent, a Lorentz transformation on a momentum-helicity
eigenstate produces a momentum-dependent phase. This phase leads to changes in
the reduced polarization density matrix, such that entanglement is either
decreased or increased, depending on the boost direction, the rapidity, and the
spread of the beam.Comment: 4 pages and 3 figures. Minor corrections, footnote on optimal basis
state
Quantum Clock Synchronization Based on Shared Prior Entanglement
We demonstrate that two spatially separated parties (Alice and Bob) can
utilize shared prior quantum entanglement, and classical communications, to
establish a synchronized pair of atomic clocks. In contrast to classical
synchronization schemes, the accuracy of our protocol is independent of Alice
or Bob's knowledge of their relative locations or of the properties of the
intervening medium.Comment: 4 page
Simulations of atomic trajectories near a dielectric surface
We present a semiclassical model of an atom moving in the evanescent field of
a microtoroidal resonator. Atoms falling through whispering-gallery modes can
achieve strong, coherent coupling with the cavity at distances of approximately
100 nanometers from the surface; in this regime, surface-induced Casmir-Polder
level shifts become significant for atomic motion and detection. Atomic transit
events detected in recent experiments are analyzed with our simulation, which
is extended to consider atom trapping in the evanescent field of a microtoroid.Comment: 29 pages, 10 figure
Quantum States of Light Produced by a High-Gain Optical Parametric Amplifier for Use in Quantum Lithography
We present a theoretical analysis of the properties of an unseeded optical parametic amplifier (OPA) used as the source of entangled photons for applications in quantum lithography. We first study the dependence of the excitation rate of a two-photon absorber on the intensity of the light leaving the OPA. We find that the rate depends linearly on intensity only for output beams so weak that they contain fewer than one photon per mode. We also study the use of an N-photon absorber for arbitrary N as the recording medium to be used with such a light source. We find that the contrast of the interference pattern and the sharpness of the fringe maxima tend to increase with increasing values of N, but that the density of fringes and thus the limiting resolution does not increase with N. We conclude that the output of an unseeded OPA exciting an N-photon absorber provides an attractive system in which to perform quantum lithography
Global talent management and staffing in MNEs: An introduction to the edited volume of international business and management
Photon polarisation entanglement from distant dipole sources
It is commonly believed that photon polarisation entanglement can only be
obtained via pair creation within the same source or via postselective
measurements on photons that overlapped within their coherence time inside a
linear optics setup. In contrast to this, we show here that polarisation
entanglement can also be produced by distant single photon sources in free
space and without the photons ever having to meet, if the detection of a photon
does not reveal its origin -- the which way information. In the case of two
sources, the entanglement arises under the condition of two emissions in
certain spatial directions and leaves the dipoles in a maximally entangled
state.Comment: 7 pages, 2 figures, revised version, accepted for publication in J.
Phys.
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