428 research outputs found
Experimental and analytical tools for evaluation of Stirling engine rod seal behavior
The first year of a two year experimental and analytical program is reported. The program is directed at the elastohydrodynamic behavior of sliding elastomeric rod seals for the Stirling engine. During the year, experimental and analytical tools were developed for evaluating seal leakage, seal friction, and the fluid film thickness at the seal/cylinder interface
Quantum Information at the Interface of Light with Atomic Ensembles and Micromechanical Oscillators
This article reviews recent research towards a universal light-matter
interface. Such an interface is an important prerequisite for long distance
quantum communication, entanglement assisted sensing and measurement, as well
as for scalable photonic quantum computation. We review the developments in
light-matter interfaces based on room temperature atomic vapors interacting
with propagating pulses via the Faraday effect. This interaction has long been
used as a tool for quantum nondemolition detections of atomic spins via light.
It was discovered recently that this type of light-matter interaction can
actually be tuned to realize more general dynamics, enabling better performance
of the light-matter interface as well as rendering tasks possible, which were
before thought to be impractical. This includes the realization of improved
entanglement assisted and backaction evading magnetometry approaching the
Quantum Cramer-Rao limit, quantum memory for squeezed states of light and the
dissipative generation of entanglement. A separate, but related, experiment on
entanglement assisted cold atom clock showing the Heisenberg scaling of
precision is described. We also review a possible interface between collective
atomic spins with nano- or micromechanical oscillators, providing a link
between atomic and solid state physics approaches towards quantum information
processing
Quantum noise limited and entanglement-assisted magnetometry
We study experimentally the fundamental limits of sensitivity of an atomic
radio-frequency magnetometer. First we apply an optimal sequence of state
preparation, evolution, and the back-action evading measurement to achieve a
nearly projection noise limited sensitivity. We furthermore experimentally
demonstrate that Einstein-Podolsky-Rosen (EPR) entanglement of atoms generated
by a measurement enhances the sensitivity to pulsed magnetic fields. We
demonstrate this quantum limited sensing in a magnetometer utilizing a truly
macroscopic ensemble of 1.5*10^12 atoms which allows us to achieve
sub-femtoTesla/sqrt(Hz) sensitivity.Comment: To appear in Physical Review Letters, April 9 issue (provisionally
Robust entanglement generation by reservoir engineering
Following a recent proposal [C. Muschik et. al., Phys. Rev. A 83, 052312
(2011)], engineered dissipative processes have been used for the generation of
stable entanglement between two macroscopic atomic ensembles at room
temperature [H. Krauter et. al., Phys. Rev. Lett. 107, 080503 (2011)]. This
experiment included the preparation of entangled states which are continuously
available during a time interval of one hour. Here, we present additional
material, further-reaching data and an extension of the theory developed in [C.
Muschik et. al., Phys. Rev. A 83, 052312 (2011)]. In particular, we show how
the combination of the entangling dissipative mechanism with measurements can
give rise to a substantial improvement of the generated entanglement in the
presence of noise.Comment: Submitted to Journal of Physics B, special issue on "Quantum Memory
Deterministic quantum teleportation between distant atomic objects
Quantum teleportation is a key ingredient of quantum networks and a building
block for quantum computation. Teleportation between distant material objects
using light as the quantum information carrier has been a particularly exciting
goal. Here we demonstrate a new element of the quantum teleportation landscape,
the deterministic continuous variable (cv) teleportation between distant
material objects. The objects are macroscopic atomic ensembles at room
temperature. Entanglement required for teleportation is distributed by light
propagating from one ensemble to the other. Quantum states encoded in a
collective spin state of one ensemble are teleported onto another ensemble
using this entanglement and homodyne measurements on light. By implementing
process tomography, we demonstrate that the experimental fidelity of the
quantum teleportation is higher than that achievable by any classical process.
Furthermore, we demonstrate the benefits of deterministic teleportation by
teleporting a dynamically changing sequence of spin states from one distant
object onto another
Entanglement generated by dissipation and steady state entanglement of two macroscopic objects
Entanglement is a striking feature of quantum mechanics and an essential
ingredient in most applications in quantum information. Typically, coupling of
a system to an environment inhibits entanglement, particularly in macroscopic
systems. Here we report on an experiment, where dissipation continuously
generates entanglement between two macroscopic objects. This is achieved by
engineering the dissipation using laser- and magnetic fields, and leads to
robust event-ready entanglement maintained for 0.04s at room temperature. Our
system consists of two ensembles containing about 10^{12} atoms and separated
by 0.5m coupled to the environment composed of the vacuum modes of the
electromagnetic field. By combining the dissipative mechanism with a continuous
measurement, steady state entanglement is continuously generated and observed
for up to an hour.Comment: This is an update of the preprint from June 2010. It includes new
results on the creation of steady state entanglement, which has been
maintained up to one hou
Sediment Mixing by Invertebrates as Shown by 85KR1
In the event radionuclides are accidentally introduced into an estuary, many isotopes would become adsorbed on suspended particles of clay or silt; others would be incorporated into living cellular material (Caritt and Goodgal, 1954; Rice and Willis, 1959). Oysters and other filter feeders in these estuaries are capable of filtering from suspension large quantities of the suspended solids, as well as the larger living cellular material (Haven and Morales-Alamo, 1966a). Ingested material along with the associated radionuclides would be voided as compacted fecal strings or pellets (biodeposits). Many of these fecal pellets may be alternately suspended in the water mass or deposited on the bottom during a single tidal cycle (Haven and Morales-Alamo, 1968).
The present paper investigates how particles in the sand or clay size range, along with adsorbed radionuclides, may be mixed into subsurface deposits
An Animal-sediment study in the lower York River : February 1965 to February 1966
Certain invertebrates are more efficient than others in filtering solids from suspension. An equal degree of variability exists among benthic invertebrates in their ability to mix biodeposits into subsurface sediments. As a result of these differences, the degree to which suspended particulate matter and associated contaminants may be deposited or mixed into sediments may in part depend on the species present, which in turn may be dependent on sediment type. A number of investigators have examined the relation between benthic animal communities and their limiting physical factors (Smith, 1932; Mare, 1942; Dexter, 1947; Holm, 1949; Stic~1ey and Stringer, 1957; Sanders, 1956, 1958, 1960; and Jones, 1961). Except for studies on the effects of thermal effluents (Warinner and Brehmer, 1966) and the relation of the distribution of several species to sediment water (Harrison and Wass, 1965), little is known of such assemblages in the Chesapeake Bay.
In this report we will examine the faunal composition at four depths in the York River, Virginia, in terms of the number of species, number of individuals and biomass, and the influence of sediment parameters on these benthic communities
The Ah domain of the mouse. Induction of proteins by the carcinogen 3-methylcholanthrene
Spin squeezing of atomic ensembles via nuclear-electronic spin entanglement
Entangled many body systems have recently attracted significant attention in
various contexts. Among them, spin squeezed atoms and ions have raised interest
in the field of precision measurements, as they allow to overcome quantum noise
of uncorrelated particles. Precise quantum state engineering is also required
as a resource for quantum computation, and spin squeezing can be used to create
multi-partite entangled states. Two-mode spin squeezed systems have been used
for elementary quantum communication protocols. Until now spin squeezing has
been always achieved via generation of entanglement between different atoms of
the ensemble. In this Letter, we demonstrate for the first time ensemble spin
squeezing generated by engineering the quantum state of each individual atom.
More specifically, we entangle the nuclear and electronic spins of
Cesium atoms at room temperature. We verify entanglement and ensemble spin
squeezing by performing quantum tomography on the atomic state.Comment: 5 pages, 3 figure
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