545 research outputs found
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
Review of \u3cem\u3eEnoch and Qumran Origins: New Light on a Forgotten Connection\u3c/em\u3e
The article reviews the book Enoch and Qumran Origins: New Light on a Forgotten Connection, edited by Gabriele Boccaccini
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
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
What matters? - Natur, Technologie und Geschlecht im Diskurs der Präimplantationsdiagnostik
Seit der Einführung der In-vitro-Fertilisation in den 1970er-Jahren sind im Feld der modernen Reproduktionsmedizin eine Reihe weiterer Verfahren entstanden, die die Vorstellungen von Zeugung und Elternschaft verändern. Leihmutterschaft, Präimplantationsdiagnostik, Eizell- und Samenspende lösen die Verbindung von Sexualität und Reproduktion und bieten ein Beispiel für die These der zunehmenden Auflösung von Körper- und Geschlechtergrenzen. Der vorliegende Beitrag leuchtet am Beispiel der Präimplantationsdiagnostik (PID) aus, wie Geschlecht und die Grenze von Natur und Technologie im Zuge dieser Entwicklung neu verhandelt werden. Anhand der Ergebnisse einer Analyse des Diskurses um die PID in Deutschland wird aufgezeigt, wie sich die PID von einer selektiven und mehrheitlich abgelehnten Diagnostik zu einer helfenden Hand für Paare mit Kinderwunsch wandelt und wie diese diskursiven Verschiebungen mit Rückgriff auf die Science and Technology Studies als eine "strategische Naturalisierung" (Thompson) und "Reinigungsarbeit" (Latour) im Diskurs verstanden werden können.New reproductive technologies have changed our understanding of pregnancy and reproduction. In vitro fertilization, preimplantation genetic diagnosis (PGD) and surrogate motherhood have created new forms of family and parenthood. As a result, reproduction is no longer solely regarded as a natural process, and the dualism of nature and technology is becoming fragile. But what kind of nature do we have instead, and what does it mean for gender boundaries? The article outlines the results of a discourse analysis of the debate around PGD in Germany. It shows how PGD is changing from a selective technology into an almost therapeutic procedure and how this change is intertwined with women’s and couples’ desire to have a healthy child. It also raises the issue of how the debate can be described from a hybrid perspective of nature and society. It is argued that the discursive shifts can be understood as a result of a “strategic naturalization” (Thompson) and "the work of purification" (Latour)
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Effect of subsurface electrical heating and steam injection on the indigenous microbial community
Since the potential for contaminant bioremediation in steam treated subsurface environments has not been explored, the thermal remedial treatment of a gasoline spill at Lawrence Livermore National Laboratory`s (LLNL) Livermore site provided an opportunity to study microbial community changes in the subsurface environment. Many terrestrial microorganisms die or become metabolically inactive if heated for a sufficient time at temperatures of 62-100{degrees}C thus thermal remediation techniques are expected to significantly alter the microbial community structure. We studied changes in community structure and population abundance as well as the characteristics of indigenous heat-tolerant microorganisms before and after steam treatment. Using fatty acid profiles from culturable microorganisms obtained from sediment cores before and after thermal treatment, a 90-98% decline in total microorganism populations in hot subsurface sediments (up to 94{degrees}C) was found. Surviving heat-tolerant microorganisms were found to possess elevated concentrations of saturated fatty acids in their lipid membranes. We also observed that some heat-tolerant microorganisms were capable of degrading gasoline compounds
High quality anti-relaxation coating material for alkali atom vapor cells
We present an experimental investigation of alkali atom vapor cells coated
with a high quality anti-relaxation coating material based on alkenes. The
prepared cells with single compound alkene based coating showed the longest
spin relaxation times which have been measured up to now with room temperature
vapor cells. Suggestions are made that chemical binding of a cesium atom and an
alkene molecule by attack to the C=C bond plays a crucial role in such
improvement of anti-relaxation coating quality
Simulating open quantum systems: from many-body interactions to stabilizer pumping
In a recent experiment, Barreiro et al. demonstrated the fundamental building
blocks of an open-system quantum simulator with trapped ions [Nature 470, 486
(2011)]. Using up to five ions, single- and multi-qubit entangling gate
operations were combined with optical pumping in stroboscopic sequences. This
enabled the implementation of both coherent many-body dynamics as well as
dissipative processes by controlling the coupling of the system to an
artificial, suitably tailored environment. This engineering was illustrated by
the dissipative preparation of entangled two- and four-qubit states, the
simulation of coherent four-body spin interactions and the quantum
non-demolition measurement of a multi-qubit stabilizer operator. In the present
paper, we present the theoretical framework of this gate-based ("digital")
simulation approach for open-system dynamics with trapped ions. In addition, we
discuss how within this simulation approach minimal instances of spin models of
interest in the context of topological quantum computing and condensed matter
physics can be realized in state-of-the-art linear ion-trap quantum computing
architectures. We outline concrete simulation schemes for Kitaev's toric code
Hamiltonian and a recently suggested color code model. The presented simulation
protocols can be adapted to scalable and two-dimensional ion-trap
architectures, which are currently under development.Comment: 27 pages, 9 figures, submitted to NJP Focus on Topological Quantum
Computatio
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