80,505 research outputs found
Generating entangled photon pairs from a cavity-QED system
We propose a scheme for the controlled generation of Einstein-Podosky-Rosen
(EPR) entangled photon pairs from an atom coupled to a high Q optical cavity,
extending the prototype system as a source for deterministic single photons. A
thorough theoretical analysis confirms the promising operating conditions of
our scheme as afforded by currently available experimental setups. Our result
demonstrates the cavity QED system as an efficient and effective source for
entangled photon pairs, and shines new light on its important role in quantum
information science.Comment: It has recently come to our attention that the experiment by T. Wilk,
S. C. Webster, A. Kuhn and G. Rempe, published in Science 317, 488 (2007),
exactly realizes what we proposed in this article, which is published in Phy.
Rev. A 040302(R) (2005
Making vortices in dipolar spinor condensates via rapid adiabatic passage
We propose to the create vortices in spin-1 condensates via magnetic
dipole-dipole interaction. Starting with a polarized condensate prepared under
large axial magnetic field, we show that by gradually inverting the field,
population transfer among different spin states can be realized in a controlled
manner. Under optimal condition, we generate a doubly quantized vortex state
containing nearly all atoms in the condensate. The resulting vortex state is a
direct manifestation of the dipole-dipole interaction and spin textures in
spinor condensates. We also point out that the whole process can be
qualitatively described by a simple rapid adiabatic passage model.Comment: 4 pages, 4 figure
Transport properties and the anisotropy of Ba_{1-x}K_xFe_2As_2 single crystals in normal and superconducting states
The transport and superconducting properties of Ba_{1-x}K_xFe_2As_2 single
crystals with T_c = 31 K were studied. Both in-plane and out-of plane
resistivity was measured by modified Montgomery method. The in-plane
resistivity for all studied samples, obtained in the course of the same
synthesis, is almost the same, unlike to the out-of plane resistivity, which
differ considerably. We have found that the resistivity anisotropy
\gamma=\rho_c /\rho_{ab} is almost temperature independent and lies in the
range 10-30 for different samples. This, probably, indicates on the extrinsic
nature of high out-of-plane resistivity, which may appear due to the presence
of the flat defects along Fe-As layers in the samples. This statement is
supported by comparatively small effective mass anisotropy, obtained from the
upper critical field measurements, and from the observation of the so-called
"Friedel transition", which indicates on the existence of some disorder in the
samples in c-direction.Comment: 5 pages, 5 figure
Magnetoelectricity and Magnetostriction due to the Rare Earth Moment in TmAl(BO)
The magnetic properties, the magnetostriction, and the magnetoelectric effect
in the d-electron free rare-earth aluminum borate TmAl(BO) are
investigated between room temperature and 2 K. The magnetic susceptibility
reveals a strong anisotropy with the hexagonal c-axis as the hard magnetic
axis. Magnetostriction measurements show a large effect of an in-plane field
reducing both, the a- and c-axis lattice parameters. The magnetoelectric
polarization change in a- and c-directions reaches up to 300 C/m at 70
kOe with the field applied along the a-axis. The magnetoelectric polarization
is proportional to the lattice contraction in magnetic field. The results of
this investigation prove the existence of a significant coupling between the
rare earth magnetic moment and the lattice in Al(BO) compounds
( = rare earth). They further show that the rare earth moment itself will
generate a large magnetoelectric effect which makes it easier to study and to
understand the origin of the magnetoelectric interaction in this class of
materials.Comment: 4 pages, 5 figure
The research progress of MSCs proliferation and differentiation in bone injury according to the TCM theory
Chinese have enjoyed not only quick recovery from but also effective daily prophylaxis of bone injuries. According to the Traditional Chinese Medicine (TCM) theory, Shen (or nephridium) is in charge of thebone, which corresponds to teeth, spine, skull, femur and the like. The function of Shen can be divided into Shen Yin (or negative nephridium) and Shen Yang (or positive nephridium). Bone injury is usuallyaccompanied with blood stasis and loss in microenvironment. Therefore, traditional Chinese doctors had chosen tonifying Shen Yin, invigorating Shen Yang, enriching and activating the blood or even combining the above three strategies for injured bone repairing. Nowadays, researchers are reunderstanding TCM drugs and formulas by studying mesenchymal stem cells (MSCs) proliferation and differentiation in vitro and vivo. This review will introduce some newest articles mainly in China focusing on the growth and differentiation of MSCs, which were treated with a single herb or formulas of those drugs (belonging to the above four classes) to demonstrate the huge potential of TCMs in thefuture bone-injury-therapeutic production of MSCs
Spin entanglement induced by spin-orbit interactions in coupled quantum dots
We theoretically explore the possibility of creating spin quantum
entanglement in a system of two electrons confined respectively in two
vertically coupled quantum dots in the presence of Rashba type spin-orbit
coupling. We find that the system can be described by a generalized Jaynes -
Cummings model of two modes bosons interacting with two spins. The lower
excitation states of this model are calculated to reveal the underlying physics
of the far infrared absorption spectra. The analytic perturbation approach
shows that an effective transverse coupling of spins can be obtained by
eliminating the orbital degrees of freedom in the large detuning limit. Here,
the orbital degrees of freedom of the two electrons, which are described by two
modes of bosons, serve as a quantized data bus to exchange the quantum
information between two electrons. Then a nontrivial two-qubit logic gate is
realized and spin entanglement between the two electrons is created by virtue
of spin-orbit coupling.Comment: 7 pages, 5 figure
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