High-fidelity conversion of photonic quantum information to telecommunication wavelength with superconducting single-photon detectors

We experimentally demonstrate a high-fidelity visible-to-telecommunication wavelength conversion of a photon by using a solid-state-based difference frequency generation. In the experiment, one half of a pico-second visible entangled photon pair at 780 nm is converted to a 1522-nm photon, resulting in the entangled photon pair between 780 nm and 1522 nm. Using superconducting single-photon detectors with low dark count rates and small timing jitters, we selectively observed well-defined temporal modes containing the two photons. We achieved a fidelity of $0.93 \pm 0.04$ after the wavelength conversion, indicating that our solid-state-based scheme can be used for faithful frequency down-conversion of visible photons emitted from quantum memories composed of various media.Comment: 5 pages, 4 figure

Ambipolar suppression of superconductivity by ionic gating in optimally-doped BaFe2(As,P)2 ultrathin films

Superconductivity (SC) in the Ba-122 family of iron-based compounds can be controlled by aliovalent or isovalent substitutions, applied external pressure, and strain, the combined effects of which are sometimes studied within the same sample. Most often, the result is limited to a shift of the SC dome to different doping values. In a few cases, the maximum SC transition at optimal doping can also be enhanced. In this work, we study the combination of charge doping together with isovalent P substitution and strain by performing ionic gating experiments on BaFe$_2$(As$_{0.8}$P$_{0.2}$)$_2$ ultrathin films. We show that the polarization of the ionic gate induces modulations to the normal-state transport properties that can be mainly ascribed to surface charge doping. We demonstrate that ionic gating can only shift the system away from the optimal conditions, as the SC transition temperature is suppressed by both electron and hole doping. We also observe a broadening of the resistive transition, which suggests that the SC order parameter is modulated nonhomogeneously across the film thickness, in contrast with earlier reports on charge-doped standard BCS superconductors and cuprates.Comment: 10 pages, 5 figure

The differences in AEP (Auditory Evoked Potentials) and SEP (Somatosensory Evoked Potentials) between epileptics and normal subjects

152 epileptics (male: 92, female: 60) and 200 normal subjects (100 of each sexes) were compared on AEP (Auditory Evoked Potential) and SEP (Somatosensory Evoked Potential), which were recorded through monopolar and bipolar derivations. The latencies and interpeak amplitudes of AEPs and VEPs were tested statistically by ANCOV A excluding the influence of age and drugs had been administered. The following results were obtained. 1. In AEPs, the latencies in epileptics were significantly longer compared with healthy subjects. These tendencies were more marked in short and middle latency components in males, but more marked in late components in females. 2. Interpeak amplitudes of AEP were relatively smaller in epileptics compared with healthy subjects. 3. In SEPs, the latencies were significantly longer in epileptics compared with healthy subjects. These tendencies were more marked in females. 4. There was no consistent tendency in interpeak amplitudes of SEP between epileptics and normal subjects in both sexes, but the interpeak amplitudes between predominant components were smaller in epileptics than normal subjects. 5. In epileptics, between the subjects had been administered the drug (each of CBZ, PB, VPA or PHT) or not, significant differences in latencies and interpeak amplitudes were not confirmed with the components significantly different in latencies and amplitudes between epileptics and healthy subjects were found. We verified the significant differences in AEP and SEP between epileptics and healthy subjects excluding the influences of age and drugs, even not considering the seizure types nor epileptic focus sites. It was supposed the disturbance in auditory and somatosensory pathway up to cortex in the central nervous system in epileptics

Density deficit of Earth’s core revealed by a multimegabar primary pressure scale

An accurate pressure scale is a fundamental requirement to understand planetary interiors. Here, we establish a primary pressure scale extending to the multimegabar pressures of Earth’s core, by combined measurement of the acoustic velocities and the density from a rhenium sample in a diamond anvil cell using inelastic x-ray scattering and x-ray diffraction. Our scale agrees well with previous primary scales and shock Hugoniots in each experimental pressure range and reveals that previous scales have overestimated laboratory pressures by at least 20% at 230 gigapascals. It suggests that the light element content in Earth’s inner core (the density deficit relative to iron) is likely to be double what was previously estimated, or Earth’s inner core temperature is much higher than expected, or some combination thereof

Nanoscale Texture and Microstructure in a NdFeAs(O,F)/IBAD-MgO Superconducting Thin Film with Superior Critical Current Properties

This paper reports the nanoscale texture and microstructure of a high-performance NdFeAs(O,F) superconducting thin film grown by molecular beam epitaxy on a textured MgO/Y2O3/Hastelloy substrate. The NdFeAs(O,F) film forms a highly textured columnar grain structure by epitaxial growth on the MgO template. Although the film contains stacking faults along the ab-plane as well as grain boundaries perpendicular to the ab-plane, good superconducting properties are measured: a critical temperature, T-c, of 46 K and a self-field critical current density, J(c), of 2 x 10(6) A/cm(2) at 4.2 K. Automated crystal orientation mapping by scanning precession electron diffraction in transmission electron microscope is employed to analyze the misorientation angles between adjacent grains in a large ensemble (247 grains), and 99% of the grain boundaries show in-plane misorientation angles (Delta gamma) less than the critical angle theta(c), which satisfies one of the necessary conditions for the high J(c). Comparing the columnar grain size distribution with the mean distance of the flux line lattice, the triple junctions of low-angle grain boundaries are found to be effective pinning centers, even at high temperatures (>= 35 K) and/or low magnetic fields

The effects of Cigarette Smoking on the human VEP (Visual Evoked Potential) and EEG

The effects of cigarette smoking on the human CNS (Central Nervous System) were studied by VEP (Visual Evoked Potential) with 38 healthy male subjects (20～42 y. o., mean : 18. 6 cig./ day×8. 5 years). All subjects were deprived of smoking from the last night prior to the expriment. In the experimental session the subjects were asked to smoke two cigarettes (nicotine content 2. 7 mg/ cig.) in ten minutes after control recording. EEGs containing VEPs evoked by flash stimuli once every 5 second were recorded into the magnetic tape through the two derivations (2CH : O1→A1+2 and 5CH : O1→Cz) together with EEGs also through four other derivations, simultaneously. Reproducing the tape, VEPs from the two derivations were recorded, with 1000 msec of analysis time, for each recording session ; before, during and 10, 20, 30 min. after cigarette smoking. The EEGs were subjected to the quantitative frequency analysis. VEPs were converted into a series of numbers and subjected to the computer processing and statistical assessment with special reference to the EEG changes. The subjects were divied into the two groups, heavy smoker group and light smoker group (more than/within 15 cig./ day), for further study. The following results were obtained. 1. In the waveforms of group mean VEP recorded from the two drivations, N4 appeared only during cigarette smoking. Latencies of P2～P4 were tended to increase during and after smoking, other latencies tended to decrease during smoking and then increased thereafter. Peak-to-peak amplitudes tended to increase, and then decrease thereafter. In the group mean VEP from 5CH, peak-to-peak amplitudes decreased during and after smoking. Conponent analysis with individual VEPs verified these changes in the group mean VEP significant. These changes in the VEPs were attributed to the early exciting (arousal) effect due to the nicotin attaining to the brain, followed by the inhibiting (sedative) effect due to the short half-life period and tachyphylaxis of nicotin. 2. The correlation coefficients between the number of cigarette smoked in one day and ratio of change of latencies and peak-to-peak amplitudes indicated that the effects of smoking above mentioned appeared more markedly with heavy smokers than with light smokers, indicating more increased susceptibility to nicotin due to cigarette abstinence with the former. 3. Quantitative frequency analysis of EEG indicated arousal effect by the decrease of θ and increase of peak α frequency, and sedative effect by the derease of β1, namely desynchronization. These" arousal sedative effect" corresponded with the VEP changes by cigarette smoking in the present study