14,328 research outputs found
Spin-mechanics with levitating ferromagnetic particles
We propose and demonstrate first steps towards schemes where the librational
mode of levitating ferromagnets is strongly coupled to the electronic spin of
Nitrogen-Vacancy (NV) centers in diamond. Experimentally, we levitate
ferromagnets in a Paul trap and employ magnetic fields to attain oscillation
frequencies in the hundreds of kHz range with Q factors close to . These
librational frequencies largely exceed the decoherence rate of NV centers in
typical CVD grown diamonds offering prospects for sideband resolved operation.
We also prepare and levitate composite diamond-ferromagnet particles and
demonstrate both coherent spin control of the NV centers and read-out of the
particle libration using the NV spin. Our results will find applications in
ultra-sensitive gyroscopy and bring levitating objects a step closer to
spin-mechanical experiments at the quantum level.Comment: Lengthened to 11 pages. To appear in PR
Quantum Repeaters with Photon Pair Sources and Multi-Mode Memories
We propose a quantum repeater protocol which builds on the well-known DLCZ
protocol [L.M. Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature 414, 413
(2001)], but which uses photon pair sources in combination with memories that
allow to store a large number of temporal modes. We suggest to realize such
multi-mode memories based on the principle of photon echo, using solids doped
with rare-earth ions. The use of multi-mode memories promises a speedup in
entanglement generation by several orders of magnitude and a significant
reduction in stability requirements compared to the DLCZ protocol.Comment: 4 pages, 2 figures, to appear in PRL, accepted versio
\u3cem\u3eArabidopsis\u3c/em\u3e AZI1 Family Proteins Mediate Signal Mobilization for Systemic Defence Priming
Priming is a major mechanism behind the immunological \u27memory\u27 observed during two key plant systemic defences: systemic acquired resistance (SAR) and induced systemic resistance (ISR). Lipid-derived azelaic acid (AZA) is a mobile priming signal. Here, we show that the lipid transfer protein (LTP)-like AZI1 and its closest paralog EARLI1 are necessary for SAR, ISR and the systemic movement and uptake of AZA in Arabidopsis. Imaging and fractionation studies indicate that AZI1 and EARLI1 localize to expected places for lipid exchange/movement to occur. These are the ER/plasmodesmata, chloroplast outer envelopes and membrane contact sites between them. Furthermore, these LTP-like proteins form complexes and act at the site of SAR establishment. The plastid targeting of AZI1 and AZI1 paralogs occurs through a mechanism that may enable/facilitate their roles in signal mobilization
Deceleration and electrostatic trapping of OH radicals
A pulsed beam of ground state OH radicals is slowed down using a Stark
decelerator and is subsequently loaded into an electrostatic trap.
Characterization of the molecular beam production, deceleration and trap
loading process is performed via laser induced fluorescence detection inside
the quadrupole trap. Depending on details of the trap loading sequence,
typically OH () radicals are trapped at a density
of around cm and at temperatures in the 50-500 mK range. The 1/e
trap lifetime is around 1.0 second.Comment: 4 pages, 3 figure
Optimal Bell tests do not require maximally entangled states
Any Bell test consists of a sequence of measurements on a quantum state in
space-like separated regions. Thus, a state is better than others for a Bell
test when, for the optimal measurements and the same number of trials, the
probability of existence of a local model for the observed outcomes is smaller.
The maximization over states and measurements defines the optimal nonlocality
proof. Numerical results show that the required optimal state does not have to
be maximally entangled.Comment: 1 figure, REVTEX
Full-Field, Carrier-Less, Polarization-Diversity, Direct Detection Receiver based on Phase Retrieval
We realize dual-polarization full-field recovery using intensity only
measurements and phase retrieval techniques based on dispersive elements.
30-Gbaud QPSK waveforms are transmitted over 520-km standard single-mode fiber
and equalized from the receiver outputs using 2X2 MIMO
Ultracompact Generation of Continuous-Variable Cluster States
We propose an experimental scheme that has the potential for large-scale
realization of continuous-variable (CV) cluster states for universal quantum
computation. We do this by mapping CV cluster-state graphs onto two-mode
squeezing graphs, which can be engineered into a single optical parametric
oscillator (OPO). The desired CV cluster state is produced directly from a
joint squeezing operation on the vacuum using a multi-frequency pump beam. This
method has potential for ultracompact experimental implementation. As an
illustration, we detail an experimental proposal for creating a four-mode
square CV cluster state with a single OPO.Comment: 4 pages, 1 figure; v2 improved discussion of the implications of our
result; added discussion of finite squeezing effect
Experimental investigation of the mechanical stiffness of periodic framework-patterned elastomers
Recent advances in the cataloguing of three-dimensional nets mean a systematic search for framework structures with specific properties is now feasible. Theoretical arguments about the elastic deformation of frameworks suggest characteristics of mechanically isotropic networks. We explore these concepts on both isotropic and anisotropic networks by manufacturing porous elastomers with three different periodic net geometries. The blocks of patterned elastomers are subjected to a range of mechanical tests to determine the dependence of elastic moduli on geometric and topological parameters. We report results from axial compression experiments, three-dimensional X-ray computed tomography imaging and image-based finite-element simulations of elastic properties of framework-patterned elastomers
The Schr\"odinger operator on an infinite wedge with a tangent magnetic field
We study a model Schr\"odinger operator with constant magnetic field on an
infinite wedge with Neumann boundary condition. The magnetic field is assumed
to be tangent to a face. We compare the bottom of the spectrum to the model
spectral quantities coming from the regular case. We are particularly motivated
by the influence of the magnetic field and the opening angle of the wedge on
the spectrum of the model operator and we exhibit cases where the bottom of the
spectrum is smaller than in the regular case. Numerical computations enlighten
the theoretical approach
How much measurement independence is needed in order to demonstrate nonlocality?
If nonlocality is to be inferred from a violation of Bell's inequality, an
important assumption is that the measurement settings are freely chosen by the
observers, or alternatively, that they are random and uncorrelated with the
hypothetical local variables. We study the case where this assumption is
weakened, so that measurement settings and local variables are at least
partially correlated. As we show, there is a connection between this type of
model and models which reproduce nonlocal correlations by allowing classical
communication between the distant parties, and a connection with models that
exploit the detection loophole. We show that even if Bob's choices are
completely independent, all correlations obtained from projective measurements
on a singlet can be reproduced, with the correlation (measured by mutual
information) between Alice's choice and local variables less than or equal to a
single bit.Comment: 5 pages, 1 figure. v2 Various improvements in presentation. Results
unchange
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