213 research outputs found
Tetra-μ-benzoato-κ8 O:O′-bis[(benzoic acid-κO)nickel(II)]
The title compound, [Ni2(C7H5O2)4(C7H6O2)2], is composed of two NiII ions, four bridging benzoate anions and two η1-benzoic acid molecules. The [Ni2(PhCOO)4] unit adopts a typical paddle-wheel conformation. The center between the two NiII atoms represents a crystallographic center of inversion. In addition, each NiII ion also coordinates to one O atom from a benzoic acid molecule. The crystal packing is realised by intermolecular hydrogen-bonding interactions and π–π stacking interactions, with a centroid–centroid distance of 3.921 (1) Å
Coherent phonon Rabi oscillations with a high frequency carbon nanotube phonon cavity
Phonon-cavity electromechanics allows the manipulation of mechanical
oscillations similar to photon-cavity systems. Many advances on this subject
have been achieved in various materials. In addition, the coherent phonon
transfer (phonon Rabi oscillations) between the phonon cavity mode and another
oscillation mode has attracted many interest in nano-science. Here we
demonstrate coherent phonon transfer in a carbon nanotube phonon-cavity system
with two mechanical modes exhibiting strong dynamical coupling. The
gate-tunable phonon oscillation modes are manipulated and detected by extending
the red-detuned pump idea of photonic cavity electromechanics. The first- and
second-order coherent phonon transfers are observed with Rabi frequencies 591
kHz and 125 kHz, respectively. The frequency quality factor product
fQ_m~2=10^12 Hz achieved here is larger thank k_B T_base/h, which may enable
the future realization of Rabi oscillations in the quantum regime
Strongly-coupled nanotube electromechanical resonators
Coupling an electromechanical resonator with carbon-nanotube quantum dots is
a significant method to control both the electronic charge and the spin quantum
states. By exploiting a novel micro-transfer technique, we fabricate two
strongly-coupled and electrically-tunable mechanical resonators on a single
carbon nanotube for the first time. The frequency of the two resonators can be
individually tuned by the bottom gates, and strong coupling is observed between
the electron charge and phonon modes of each resonator. Furthermore, the
conductance of either resonator can be nonlocally modulated by the phonon modes
in the other resonator. Strong coupling is observed between the phonon modes of
the two resonators, which provides an effective long distance electron-electron
interaction. The generation of phonon-mediated-spin entanglement is also
theoretically analyzed for the two resonators. This strongly-coupled nanotube
electromechanical resonator array provides an experimental platform for future
studies of the coherent electron-phonon interaction, the phonon mediated
long-distance electron interaction, and entanglement state generation
Storage of 1650 modes of single photons at telecom wavelength
To advance the full potential of quantum networks one should be able to
distribute quantum resources over long distances at appreciable rates. As a
consequence, all components in the networks need to have large multimode
capacity to manipulate photonic quantum states. Towards this end, a multimode
photonic quantum memory, especially one operating at telecom wavelength,
remains a key challenge. Here we demonstrate a spectro-temporally multiplexed
quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded
single photons is realized by employing the atomic frequency comb protocol in a
10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing
encompasses five spectral channels - each 10 GHz wide - and in each of these up
to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of
single photons. Our demonstrations open doors for high-rate quantum networks,
which are essential for future quantum internet
Theory and Experiments of Pressure-Tunable Broadband Light Emission from Self-Trapped Excitons in Metal Halide Crystals
Hydrostatic pressure has been commonly applied to tune broadband light
emissions from self-trapped excitons (STE) in perovskites for producing white
light and study of basic electron-phonon interactions. However, a general
theory is still lacking to understand pressure-driven evolution of STE
emissions. In this work we first identify a theoretical model that predicts the
effect of hydrostatic pressure on STE emission spectrum, we then report the
observation of extremely broadband photoluminescence emission and its wide
pressure spectral tuning in 2D indirect bandgap CsPb2Br5 crystals. An excellent
agreement is found between the theory and experiment on the peculiar
experimental observation of STE emission with a nearly constant spectral
bandwidth but linearly increasing energy with pressure below 2 GPa. Further
analysis by the theory and experiment under higher pressure reveals that two
types of STE are involved and respond differently to external pressure. We
subsequently survey published STE emissions and discovered that most of them
show a spectral blue-shift under pressure, as predicted by the theory. The
identification of an appropriate theoretical model and its application to STE
emission through the coordinate configuration diagram paves the way for
engineering the STE emission and basic understanding of electron-phonon
interaction
Effect of dispersion on indistinguishability between single-photon wave-packets
With propagating through a dispersive medium, the temporal-spectral profile
of laser pulses should be inevitably modified. Although such dispersion effect
has been well studied in classical optics, its effect on a single-photon
wave-packet, i.e., the matter wave of a single-photon, has not yet been
entirely revealed. In this paper, we investigate the effect of dispersion on
indistinguishability of single-photon wave-packets through the Hong-Ou-Mandel
(HOM) interference. By dispersively manipulating two indistinguishable
single-photon wave-packets before interfering with each other, we observe that
the difference of the second-order dispersion between two optical paths of the
HOM interferometer can be mapped to the interference curve, indicating that (1)
with the same amount of dispersion effect in both paths, the HOM interference
curve must be only determined by the intrinsic indistinguishability between the
wave-packets, i.e., dispersion cancellation due to the indistinguishability
between Feynman paths; (2) unbalanced dispersion effect in two paths cannot be
cancelled and will broaden the interference curve thus providing a way to
measure the second-order dispersion coefficient. Our results suggest a more
comprehensive understanding of the single-photon wave-packet and pave ways to
explore further applications of the HOM interference
The capsid protein p38 of turnip crinkle virus is associated with the suppression of cucumber mosaic virus in Arabidopsis thaliana co-infected with cucumber mosaic virus and turnip crinkle virus
AbstractInfection of plants by multiple viruses is common in nature. Cucumber mosaic virus (CMV) and Turnip crinkle virus (TCV) belong to different families, but Arabidopsis thaliana and Nicotiana benthamiana are commonly shared hosts for both viruses. In this study, we found that TCV provides effective resistance to infection by CMV in Arabidopsis plants co-infected by both viruses, and this antagonistic effect is much weaker when the two viruses are inoculated into different leaves of the same plant. However, similar antagonism is not observed in N. benthamiana plants. We further demonstrate that disrupting the RNA silencing-mediated defense of the Arabidopsis host does not affect this antagonism, but capsid protein (CP or p38)-defective mutant TCV loses the ability to repress CMV, suggesting that TCV CP plays an important role in the antagonistic effect of TCV toward CMV in Arabidopsis plants co-infected with both viruses
High-quality multi-wavelength quantum light sources on silicon nitride micro-ring chip
Multi-wavelength quantum light sources, especially at telecom band, are
extremely desired in quantum information technology. Despite recent impressive
advances, such a quantum light source with high quality remains challenging.
Here we demonstrate a multi-wavelength quantum light source using a silicon
nitride micro-ring with a free spectral range of 200 GHz. The generation of
eight pairs of correlated photons is ensured in a wavelength range of 25.6 nm.
With device optimization and noise-rejecting filters, our source enables the
generation of heralded single-photons - at a rate of 62 kHz with
, and the generation of energy-time entangled
photons - with a visibility of in the Franson interferometer.
These results, at room temperature and telecom wavelength, in a CMOS compatible
platform, represent an important step towards integrated quantum light devices
for the quantum networks.Comment: 7 pages, 4 figure
Energy-time Entanglement Coexisting with Fiber Optical Communication at Telecom C-band
The coexistence of quantum and classical light in the same fiber link is
extremely desired in developing quantum communication. It has been implemented
for different quantum information tasks, such as classical light coexisting
with polarization-entangled photons at telecom O-band, and with quantum signal
based quantum key distribution (QKD). In this work, we demonstrate the
coexistence of energy-time entanglement based QKD and fiber optical
communication at the telecom C-band. The property of noise from the classical
channel is characterized with classical light at different wavelengths. With
the largest noise, i.e., the worst case, the properties of energy-time
entanglement are measured at different fiber optical communication rates. By
measuring the two-photon interference of energy-time entanglement, our results
show that a visibility of 82.011.10\% is achieved with a bidirectional 20
Gbps fiber optical communication over 40 km. Furthermore, by performing the
BBM92 protocol for QKD, a secret key rate of 245 bits per second could be
generated with a quantum bit error rate of 8.88\% with the coexisted
energy-time entanglement.~Our demonstration paves the way for developing the
infrastructure for quantum networks compatible with fiber optical
communication.Comment: 6 pages, 3 figures
Discovering multiple transcripts of human hepatocytes using massively parallel signature sequencing (MPSS)
<p>Abstract</p> <p>Background</p> <p>The liver is the largest human internal organ – it is composed of multiple cell types and plays a vital role in fulfilling the body's metabolic needs and maintaining homeostasis. Of these cell types the hepatocytes, which account for three-quarters of the liver's volume, perform its main functions. To discover the molecular basis of hepatocyte function, we employed Massively Parallel Signature Sequencing (MPSS) to determine the transcriptomic profile of adult human hepatocytes obtained by laser capture microdissection (LCM).</p> <p>Results</p> <p>10,279 UniGene clusters, representing 7,475 known genes, were detected in human hepatocytes. In addition, 1,819 unique MPSS signatures matching the antisense strand of 1,605 non-redundant UniGene clusters (such as <it>APOC1</it>, <it>APOC2</it>, <it>APOB </it>and <it>APOH</it>) were highly expressed in hepatocytes.</p> <p>Conclusion</p> <p>Apart from a large number of protein-coding genes, some of the antisense transcripts expressed in hepatocytes could play important roles in transcriptional interference via a <it>cis</it>-/<it>trans</it>-regulation mechanism. Our result provided a comprehensively transcriptomic atlas of human hepatocytes using MPSS technique, which could be served as an available resource for an in-depth understanding of human liver biology and diseases.</p
- …