Optical spectroscopy study on single crystalline LaFeAsO

Millimeter-sized single crystals of LaFeAsO were grown from NaAs flux and the in-plane optical properties were studied over a wide frequency range. A sizable electronic correlation effect was indicated from the analysis of the free-carrier spectral weight. With decreasing temperature from 300 K, we observed a continuous suppression of the spectral weight near 0.6 eV. But a spin-density-wave gap formation at lower energy scale was seen only in the broken-symmetry state. We elaborate that both the itinerancy and local spin interactions of Fe\emph{3d} electrons are present for the FeAs-based systems; however, the establishment of the long-range magnetic order at low temperature has a dominantly itinerant origin.Comment: 4 figures, 5 page

Quantum key distribution over 122 km of standard telecom fiber

We report the first demonstration of quantum key distribution over a standard telecom fiber exceeding 100 km in length. Through careful optimisation of the interferometer and single photon detector, we achieve a quantum bit error ratio of 8.9% for a 122km link, allowing a secure shared key to be formed after error correction and privacy amplification. Key formation rates of up to 1.9 kbit/sec are achieved depending upon fiber length. We discuss the factors limiting the maximum fiber length in quantum cryptography

Quantum computing through electron propagation in the edge states of quantum spin Hall systems

We propose to implement quantum computing based on electronic spin qubits by controlling the propagation of the electron wave packets through the helical edge states of quantum spin Hall systems (QSHs). Specfically, two non-commutative single-qubit gates, which rotate a qubit around z and y axes, can be realized by utilizing gate voltages either on a single QSH edge channel or on a quantum point contact structure. The more challenging two-qubit controlled phase gate can be implemented through the on-demand capacitive Coulomb interaction between two adjacent edge channels from two parallel QSHs. As a result, a universal set of quantum gates can be achieved in an all-electrical way. The fidelity and purity of the two-qubit gate are calculated with both time delay and finite width of the wave packets taken into consideration, which can reach high values with the existing high-quality single electron source

Photovoltaic Oscillations Due to Edge-Magnetoplasmon Modes in a Very-High Mobility 2D Electron Gas

Using very-high mobility GaAs/AlGaAs 2D electron Hall bar samples, we have experimentally studied the photoresistance/photovoltaic oscillations induced by microwave irradiation in the regime where both 1/B and B-periodic oscillations can be observed. In the frequency range between 27 and 130 GHz we found that these two types of oscillations are decoupled from each other, consistent with the respective models that 1/B oscillations occur in bulk while the B-oscillations occur along the edges of the Hall bars. In contrast to the original report of this phenomenon (Ref. 1) the periodicity of the B-oscillations in our samples are found to be independent of L, the length of the Hall bar section between voltage measuring leads.Comment: 4 pages, 4 figure

Generation and characterization of a monoclonal antibody to penicillic acid from Penicillium cyclopium

Penicillic acid is one of the main mycotoxins in moldy feedstuff and has toxic effect on livestock and poultry and probably humans due to food chain transmission. The objective of this study was to generate and characterize a monoclonal antibody to penicillic acid for the efficient detection of penicillic acid from Penicillium cyclopium by immunological methods. To this end, penicillic acid was conjugated to bovine serum album (BSA) using the Mannich reaction and coupled with ovalbumin(OVA) by the method of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide hydrochloride (EDC) to generate artificial antigens penicillic acid-BSA and penicillic acid-OVA. A hybridoma cell line was obtained after fusion of mouse SP2/0 myeloma cells with spleen cells of BALB/c mice immunized with artificial antigen penicillic acid-BSA. A monoclonal antibody specific against penicillic acid was produced in vivo by this hybridoma cell line. Further analysis revealed that the monoclonal antibody to penicillic acid was of the IgG1 subtype, with a titer of 1: 2.05 × 105. The antibody to penicillic acid had no or less cross-reaction with mycotoxins, including aflatoxin B1, zearalenone, T-2 toxin and fumonisins and more importantly, it assumed an affinity of about 1.54 × 108 liters per mol. Our ability to produce a monoclonal antibody to penicillic acid provides necessary groundwork for the effective detection of penicillic acid in various tissues of animals and human, using the immunocytochemistry,Western blots and enzyme-linked immunosorbent assay (ELISA)