2,227 research outputs found
Continuous loading of S calcium atoms into an optical dipole trap
We demonstrate an efficient scheme for continuous trap loading based upon
spatially selective optical pumping. We discuss the case of S
calcium atoms in an optical dipole trap (ODT), however, similar strategies
should be applicable to a wide range of atomic species. Our starting point is a
reservoir of moderately cold (K) metastable
P-atoms prepared by means of a magneto-optic trap (triplet-MOT). A
focused 532 nm laser beam produces a strongly elongated optical potential for
S-atoms with up to 350 K well depth. A weak focused laser beam
at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the
P-atoms inside the capture volume to the singlet state, where they
are confined by the ODT. The triplet-MOT perpetually refills the capture volume
with P-atoms thus providing a continuous stream of cold atoms into
the ODT at a rate of s. Limited by evaporation loss, in 200 ms we
typically load atoms with an initial radial temperature of 85
K. After terminating the loading we observe evaporation during 50 ms
leaving us with atoms at radial temperatures close to 40 K and a
peak phase space density of . We point out that a
comparable scheme could be employed to load a dipole trap with
P-atoms.Comment: 4 pages, 4 figure
Integrated optical source of polarization entangled photons at 1310 nm
We report the realization of a new polarization entangled photon-pair source
based on a titanium-indiffused waveguide integrated on periodically poled
lithium niobate pumped by a CW laser at . The paired photons are
emitted at the telecom wavelength of within a bandwidth of .
The quantum properties of the pairs are measured using a two-photon coalescence
experiment showing a visibility of 85%. The evaluated source brightness, on the
order of pairs , associated with its
compactness and reliability, demonstrates the source's high potential for
long-distance quantum communication.Comment: There is a typing mistake in the previous version in the visibility
equation. This mistake doesn't change the result
Detector imperfections in photon-pair source characterization
We analyze how imperfections in single-photon detectors impact the
characterization of photon-pair sources. We perform exact calculations to
reveal the effects of multi-pair emissions and of noisy, non-unit efficiency,
non photon-number resolving detections on the Cauchy-Schwarz parameter, on the
second order auto-correlation and cross-correlation functions, and on the
visibilities of both Hong-Ou-Mandel and Bell-like interferences. We consider
sources producing either two-mode squeezed states or states with a Poissonian
photon distribution. The proposed formulas are useful in practice to determine
the impacts of multi-pair emissions and dark counts in standard tests used in
quantum optics.Comment: 9 pages, 11 figure
Photon-bunching measurement after 2x25km of standard optical fibers
To show the feasibility of a long distance partial Bell-State measurement, a
Hong-Ou-Mandel experiment with coherent photons is reported. Pairs of
degenerate photons at telecom wavelength are created by parametric down
conversion in a periodically poled lithium niobate waveguide. The photon pairs
are separated in a beam-splitter and transmitted via two fibers of 25km. The
wave-packets are relatively delayed and recombined on a second beam-splitter,
forming a large Mach-Zehnder interferometer. Coincidence counts between the
photons at the two output modes are registered. The main challenge consists in
the trade-off between low count rates due to narrow filtering and length
fluctuations of the 25km long arms during the measurement. For balanced paths a
Hong-Ou-Mandel dip with a visibility of 47.3% is observed, which is close to
the maximal theoretical value of 50% developed here. This proves the
practicability of a long distance Bell state measurement with two independent
sources, as e.g. required in an entanglement swapping configuration in the
scale of tens of km.Comment: 6 pages, 5 figure
Similarity solutions and Conservation laws for the Bogoyavlensky-Konopelchenko Equation by Lie point symmetries
The 1 + 2 dimensional Bogoyavlensky-Konopelchenko Equation is investigated
for its solution and conservation laws using the Lie point symmetry analysis.
In the recent past, certain work has been done describing the Lie point
symmetries for the equation and this work seems to be incomplete (Ray S (2017)
Compt. Math. Appl. 74, 1157). We obtained certain new symmetries and
corresponding conservation laws. The travelling-wave solution and some other
similarity solutions are studied.Comment: 12 pages. Accepted for publication in Quaestiones Mathematica
Gastric Follicular Dendritic Cell Sarcoma: A Case Report of a Rare Entity
Follicular Dendritic cell sarcoma arises from the follicular dendritic cells present in the lymphnode.Though are commonly seen in head and neck area but are extremely rare in the abdomen. Less than eighty cases are reported in the indexed literature. We herein describe a case of follicular dendritic cell sarcoma arising from the stomach wall with infiltration into pancreas in an 85 year old patient
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