238 research outputs found
Transmission area and two-photon correlated imaging
The relationship between transmission area of an object imaged and the
visibility of its image is investigated in a lensless system. We show that the
changes of the visibility are quite different when the transmission area is
varied by different manners. An increase of the transmission by adding the slit
number leads to a decrease of the visibility. While, the change is adverse when
the slit width is widened for a given distance between two slits.Comment: 10 pages, 4 figure
Sub-wavelength Coherent Imaging of a Pure-Phase Object with Thermal Light
We report, for the first time, the observation of sub-wavelength coherent
image of a pure phase object with thermal light,which represents an accurate
Fourier transform. We demonstrate that ghost-imaging scheme (GI) retrieves
amplitude transmittance knowledge of objects rather than the transmitted
intensities as the HBT-type imaging scheme does.Comment: 5 pages, 4 figures; Any comments pls. contact: [email protected]
Dirac quantum spin liquid emerging in a kagome-lattice antiferromagnet
Emerging quasi-particles with Dirac dispersion in condensed matter physics
are analogous to their cousins in high-energy physics in that both of them can
be described by the Dirac equation for relativistic electrons. Recently, these
Dirac fermions have been widely found in electronic systems, such as graphene
and topological insulators. At the conceptual level, since the charge is not a
prerequisite for Dirac fermions, the emergence of Dirac fermions without charge
degree of freedom has been theoretically predicted to be realized in Dirac
quantum spin liquids. In such case, the Dirac quasiparticles are charge-neutral
and carry a spin of 1/2, known as spinons. Despite of theoretical aspirations,
spectra evidence of Dirac spinons remains elusive. Here we show that the spin
excitations of a kagome antiferromagnet,
YCu(OD)Br[Br(OD)], are conical with a spin continuum
inside, which are consistent with the convolution of two Dirac spinons. The
spinon velocity obtained from the spin excitations also quantitatively
reproduces the low-temperature specific heat of the sample. Interestingly, the
locations of the conical spin excitations differ from those calculated by the
nearest neighbor Heisenberg model, suggesting an unexpected origin of the Dirac
spinons. Our results thus provide strong spectra evidence for the Dirac
quantum-spin-liquid state emerging in this kagome-lattice antiferromagnet.Comment: 7 pages, 4 figure
Lensless Fourier-Transform Ghost Imaging with Classical Incoherent Light
The Fourier-Transform ghost imaging of both amplitude-only and pure-phase
objects was experimentally observed with classical incoherent light at Fresnel
distance by a new lensless scheme. The experimental results are in good
agreement with the standard Fourier-transform of the corresponding objects.
This scheme provides a new route towards aberration-free diffraction-limited 3D
images with classically incoherent thermal light, which have no resolution and
depth-of-field limitations of lens-based tomographic systems.Comment: 14 pages, 4 figures, comments are welcom
SARS-CoV Infection in a Restaurant from Palm Civet
Contact with food animals was associated with SARS-CoV infection in the People’s Republic of China
- …