236 research outputs found
Non-destructive interferometric characterization of an optical dipole trap
A method for non-destructive characterization of a dipole trapped atomic
sample is presented. It relies on a measurement of the phase-shift imposed by
cold atoms on an optical pulse that propagates through a free space
Mach-Zehnder interferometer. Using this technique we are able to determine,
with very good accuracy, relevant trap parameters such as the atomic sample
temperature, trap oscillation frequencies and loss rates. Another important
feature is that our method is faster than conventional absorption or
fluorescence techniques, allowing the combination of high-dynamical range
measurements and a reduced number of spontaneous emission events per atom.Comment: 9 pages, 6 figures, submitted to PR
Non-Destructive Probing of Rabi Oscillations on the Cesium Clock Transition near the Standard Quantum Limit
We report on non-destructive observation of Rabi oscillations on the Cs clock
transition. The internal atomic state evolution of a dipole-trapped ensemble of
cold atoms is inferred from the phase shift of a probe laser beam as measured
using a Mach-Zehnder interferometer. We describe a single color as well as a
two-color probing scheme. Using the latter, measurements of the collective
pseudo-spin projection of atoms in a superposition of the clock states are
performed and the observed spin fluctuations are shown to be close to the
standard quantum limit.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Highly multimode memory in a crystal
We experimentally demonstrate the storage of 1060 temporal modes onto a
thulium-doped crystal using an atomic frequency comb (AFC). The comb covers
0.93 GHz defining the storage bandwidth. As compared to previous AFC
preparation methods (pulse sequences i.e. amplitude modulation), we only use
frequency modulation to produce the desired optical pumping spectrum. To ensure
an accurate spectrally selective optical pumping, the frequency modulated laser
is self-locked on the atomic comb. Our approach is general and should be
applicable to a wide range of rare-earth doped material in the context of
multimode quantum memory
Rotating Higher Spin Partition Functions and Extended BMS Symmetries
We evaluate one-loop partition functions of higher-spin fields in thermal
flat space with angular potentials; this computation is performed in arbitrary
space-time dimension, and the result is a simple combination of Poincar\'e
characters. We then focus on dimension three, showing that suitable products of
one-loop partition functions coincide with vacuum characters of higher-spin
asymptotic symmetry algebras at null infinity. These are extensions of the
bms_3 algebra that emerges in pure gravity, and we propose a way to build their
unitary representations and to compute the associated characters. We also
extend our investigations to supergravity and to a class of gauge theories
involving higher-spin fermionic fields.Comment: 58 pages; clarifications and references added; version to be
published in JHE
Evaluation of classical precipitation descriptions for γ′′(Ni3Nb−D022) in Ni-base superalloys
The growth/coarsening kinetics of γ′′(Ni3Nb−D022) precipitates have been found by numerous researchers to show an apparent correspondence with the classical (Ostwald ripening) equation outlined by Lifshitz, Slyozov and (separately) Wagner for a diffusion controlled regime. Nevertheless, a significant disparity between the actual precipitate size distribution shape and that predicted by LSW is frequently observed in the interpretation of these results, the origin of which is unclear. Analysis of the literature indicates one likely cause for this deviation from LSW for γ′′ precipitates is the “encounter” phenomenon described by Davies et al. (Acta Metall 28(2):179–189, 1980) that is associated with secondary phases comprising a high volume fraction. Consequently, the distributions of both γ′′ precipitates described in the literature (Alloy 718) and measured in this research in Alloy 625 are analysed through employing the Lifshitz–Slyozov-Encounter-Modified (LSEM) formulation (created by Davies et al.). The results of the LSEM analysis show good far better agreement than LSW with experimental distributions after the application of a necessary correction for what is termed in this research as “directional encounter”. Moreover, the activation energy for γ′′ coarsening in Alloy 625 shows conformity with literature data once the effect of heterogeneous (on dislocations) precipitate nucleation at higher temperatures is accounted for
Extensive arterial and venous thrombo-embolism with chemotherapy for testicular cancer: a case report
Germ cell tumours tend to affect young adults and with advanced treatments achieve more than 90% cure rates. Over the years cisplatin has significantly improved the relapse free survival in these patients, hence forming an essential component of chemotherapy regimes. But, the thrombo-embolic complications suffered with cisplatin significantly affect the quality of life in these young patients
Teleportation Systems Toward a Quantum Internet
Quantum teleportation is essential for many quantum information technologies, including long-distance quantum networks. Using fiber-coupled devices, including state-of-the-art low-noise superconducting nanowire single-photon detectors and off-the-shelf optics, we achieve conditional quantum teleportation of time-bin qubits at the telecommunication wavelength of 1536.5 nm. We measure teleportation fidelities of ≥90% that are consistent with an analytical model of our system, which includes realistic imperfections. To demonstrate the compatibility of our setup with deployed quantum networks, we teleport qubits over 22 km of single-mode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are compatible with emerging solid-state quantum devices, provide a realistic foundation for a high-fidelity quantum Internet with practical devices
Teleportation Systems Toward a Quantum Internet
Quantum teleportation is essential for many quantum information technologies, including long-distance quantum networks. Using fiber-coupled devices, including state-of-the-art low-noise superconducting nanowire single-photon detectors and off-the-shelf optics, we achieve conditional quantum teleportation of time-bin qubits at the telecommunication wavelength of 1536.5 nm. We measure teleportation fidelities of ≥90% that are consistent with an analytical model of our system, which includes realistic imperfections. To demonstrate the compatibility of our setup with deployed quantum networks, we teleport qubits over 22 km of single-mode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are compatible with emerging solid-state quantum devices, provide a realistic foundation for a high-fidelity quantum Internet with practical devices
The Palomar Testbed Interferometer Calibrator Catalog
The Palomar Testbed Interferometer (PTI) archive of observations between 1998
and 2005 is examined for objects appropriate for calibration of optical
long-baseline interferometer observations - stars that are predictably
point-like and single. Approximately 1,400 nights of data on 1,800 objects were
examined for this investigation. We compare those observations to an
intensively studied object that is a suitable calibrator, HD217014, and
statistically compare each candidate calibrator to that object by computing
both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis
is that the frequency distribution of visibility data associated with
calibrator stars differs from non-calibrator stars such as binary stars.
Spectroscopic binaries resolved by PTI, objects known to be unsuitable for
calibrator use, are similarly tested to establish detection limits of this
approach. From this investigation, we find more than 350 observed stars
suitable for use as calibrators (with an additional being
rejected), corresponding to sky coverage for PTI. This approach
is noteworthy in that it rigorously establishes calibration sources through a
traceable, empirical methodology, leveraging the predictions of spectral energy
distribution modeling but also verifying it with the rich body of PTI's on-sky
observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n
Sensitivity of a tonne-scale NEXT detector for neutrinoless double beta decay searches
The Neutrino Experiment with a Xenon TPC (NEXT) searches for the neutrinoless
double-beta decay of Xe-136 using high-pressure xenon gas TPCs with
electroluminescent amplification. A scaled-up version of this technology with
about 1 tonne of enriched xenon could reach in less than 5 years of operation a
sensitivity to the half-life of neutrinoless double-beta decay decay better
than 1E27 years, improving the current limits by at least one order of
magnitude. This prediction is based on a well-understood background model
dominated by radiogenic sources. The detector concept presented here represents
a first step on a compelling path towards sensitivity to the parameter space
defined by the inverted ordering of neutrino masses, and beyond.Comment: 22 pages, 11 figure
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