Heralded entanglement distribution between two absorptive quantum memories.

Owing to the inevitable loss in communication channels, the distance of entanglement distribution is limited to approximately 100 kilometres on the ground1. Quantum repeaters can circumvent this problem by using quantum memory and entanglement swapping2. As the elementary link of a quantum repeater, the heralded distribution of two-party entanglement between two remote nodes has only been realized with built-in-type quantum memories3-9. These schemes suffer from the trade-off between multiplexing capacity and deterministic properties and hence hinder the development of efficient quantum repeaters. Quantum repeaters based on absorptive quantum memories can overcome such limitations because they separate the quantum memories and the quantum light sources. Here we present an experimental demonstration of heralded entanglement between absorptive quantum memories. We build two nodes separated by 3.5 metres, each containing a polarization-entangled photon-pair source and a solid-state quantum memory with bandwidth up to 1 gigahertz. A joint Bell-state measurement in the middle station heralds the successful distribution of maximally entangled states between the two quantum memories with a fidelity of 80.4 ± 2.2 per cent (±1 standard deviation). The quantum nodes and channels demonstrated here can serve as an elementary link of a quantum repeater. Moreover, the wideband absorptive quantum memories used in the nodes are compatible with deterministic entanglement sources and can simultaneously support multiplexing, which paves the way for the construction of practical solid-state quantum repeaters and high-speed quantum networks.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology.

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.

Prognostic significance of Nemo-like kinase expression in patients with hepatocellular carcinoma.

Nemo-like kinase (NLK) is an evolutionarily conserved serine/threonine protein kinase and belongs to the extracellular signal-regulated kinases/microtubule-associated protein kinase families (Erks/MAPKs). Previous studies have indicated that abnormal expressions of NLK played critical roles in various types of human cancers. Recent studies suggested that NLK expression was significantly upregulated in the hepatocellular carcinoma (HCC) specimens. However, the clinical significance of NLK expression in HCC remains largely unknown. In this study, we focused on the clinical significance of NLK in HCC and found that high expression of NLK was significantly associated with Edmondson-Steiner grade (P = 0.002), tumor size (P = 0.022), and no. of tumor nodules (P < 0.001), and NLK was positively correlated with proliferation marker Ki-67 (P < 0.01). Univariate analysis suggested that NLK expression was associated with poor prognosis (P < 0.001). Multivariate analysis indicated that NLK expression was an independent prognostic indicator for HCC (P = 0.0370). In conclusion, NLK overexpression is associated with poor overall survival in patients with HCC, it might be an independent poor prognostic marker for HCC.

Storage of telecom-C-band heralded single photons with orbital-angular-momentum encoding in a crystal.

A memory-based quantum repeater architecture provides a solution to distribute quantum information to an arbitrary long distance. Practical quantum repeaters are likely to be built in optical-fiber networks which take advantage of the low-loss transmission between quantum memory nodes. Most quantum memory platforms have characteristic atomic transitions away from the telecommunication band. A nondegenerate photon pair source is therefore useful for connection of a quantum memory to optical fibers. Here, we report a high-brightness narrowband photon-pair source which is compatible with a rare-earth-ion-doped crystal Pr3+:Y2SiO5. The photon-pair source is generated through a cavity-enhanced spontaneous parametric down-conversion process with the signal photon at 606 nm and the idler photon at 1540 nm. Moreover, using the telecom C-band idler photons for heralding, we demonstrate the reversible transfer of orbital-angular-momentum qubit between the signal photon and the quantum memory based on Pr3+:Y2SiO5.

Multiplexed storage and real-time manipulation based on a multiple degree-of-freedom quantum memory.

The faithful storage and coherent manipulation of quantum states with matter-systems would enable the realization of large-scale quantum networks based on quantum repeaters. To achieve useful communication rates, highly multimode quantum memories are required to construct a multiplexed quantum repeater. Here, we present a demonstration of on-demand storage of orbital-angular-momentum states with weak coherent pulses at the single-photon-level in a rare-earth-ion-doped crystal. Through the combination of this spatial degree-of-freedom (DOF) with temporal and spectral degrees of freedom, we create a multiple-DOF memory with high multimode capacity. This device can serve as a quantum mode converter with high fidelity, which is a fundamental requirement for the construction of a multiplexed quantum repeater. This device further enables essentially arbitrary spectral and temporal manipulations of spatial-qutrit-encoded photonic pulses in real time. Therefore, the developed quantum memory can serve as a building block for scalable photonic quantum information processing architectures.

Study on the inclusion behavior between meso-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide and beta-cyclodextrin derivatives in aqueous solution.

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide (TPPOC3Py), with beta-CD and HP-beta-CD in aqueous solution has been studied by UV-vis, 1H NMR, 2D-NOESY and MALDI-TOF MS, and it reveals that a stable 1:1 inclusion complex between TPPOC3Py and HP-beta-CD or beta-CD has formed, in which one of the meso substituents of porphyrin ring has deeply penetrated through the cavity of HP-beta-CD from secondary face. The inclusion constants of the complexes of TPPOC3Py-beta-CD and TPPOC3Py-HP-beta-CD are (1.6+/-0.2)x10(3) M-1 and (8.9+/-0.4)x10(4) M-1, respectively.

Interaction of water-soluble cationic porphyrin with anionic surfactant.

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis [4-(3-pyridiniumpropoxy)phenyl]porphyrin tetrakisbromide (TPPOC3Py), with anionic surfactant, sodium dodecyl sulfate (SDS), in aqueous solution has been studied by means of UV-vis, (1)H NMR, fluorescence, circular dichroism (CD) spectra and dynamic laser light scattering (DLLS), and it reveals that TPPOC3Py forms porphyrin-surfactant complexes (aggregates), including ordered structures J- and H-aggregates, induced by association with surfactant monomers below the SDS critical micelle concentration (cmc), and forms micellized monomer upon the cmc, respectively. The position of TPPOC3Py in the micelle is determined, which is not in the micelle core instead of intercalated among the SDS chains, most likely with the pyridinium group extending into the polar headgroup region of the micelle.

[Effects of different application amount of N, P, K fertilizers on physiological characteristics, yield and kernel quality of peanut].

The field experiment was executed with peanut cv. Fenghua No. 1 from 2004 to 2005 in the experimental station of Shandong Agricultural University to study the effects of N, P, K fertilizers application amount on physiological characteristics, yield and kernel quality of peanut. The results showed that, compared with no fertilization, application N, P, K fertilizers increased the content of chlorophyll and soluble protein, enhanced photosynthetic rate and the activities of superoxide dismutase (SOD), peroxidase (POD) and catlase (CAT), and reduced malondialdeyde (MDA) accumulation amount in peanut leaves. The effects of applying N 300-450 kg x hm(-2), P5O2, 150-225 kg x hm(-2) and K2O 300-450 kg x hm(-2) treatments were the most significant. The improvement effect of N fertilizer on photosynthesis properties was mainly at early stage, and that of P was at middle-later stage, K was at whole stage. Applying N, P, K fertilizers increased the pod yield of peanut remarkably, and with the increasing of N application amount the pod yield enhanced, the pod yields were highest when P and K application were at middle amount rates (P5O2, 150 kg x hm(-2) K2O 300 kg x hm(-2)). The increasing effect on pod yield of K fertilizer was greater than that of N and P fertilizers. Applying a small amount of P and K fertilizers (P2O5 75 kg x hm(-2), K2O 150 kg x hm(-2)) could significantly increase the contents of fat and protein in peanut kernel, applying a small amount of N fertilizer (N 150 kg x hm(-2)) could significantly increase the content of protein in peanut kernel, but applying a large amount of N fertilizer (N 450 kg x hm(-2)) could significantly increase the content of fat in peanut kernel. Applying P fertilizer obviously increased fat and protein content, applying N fertilizer mainly enhanced protein content, and applying K fertilizer mainly raised the content of soluble sugar. In addition, the application of N, P and K fertilizers also increased the contents of lysine and methionine which were inadequate in the protein fractions of peanut kernel, enhanced the contents of oleic acid and linoleic acid, raised the ratio of oleic acid to linoleic acid, improved nutritional quality of peanut, and pronged the shelf life of peanut products.