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Entanglement is one of the key features of quantum information and communications technology. The method that has been used most frequently to generate highly entangled pairs of photons1,2 is parametric down-conversion. Short-wavelength entangled photons are desirable for generating further entanglement between three or four photons, but it is difficult to use parametric down-conversion to generate suitably energetic entangled photon pairs. One method that is expected to be applicable for the generation of such photons3 is resonant hyper-parametric scattering (RHPS): a pair of entangled photons is generated in a semiconductor via an electronically resonant third-order nonlinear optical process. Semiconductor-based sources of entangled photons would also be advantageous for practical quantum technologies, but attempts to generate entangled photons in semiconductors have not yet been successful4,5. Here we report experimental evidence for the generation of ultraviolet entangled photon pairs by means of biexciton resonant RHPS in a single crystal of the semiconductor CuCl. We anticipate that our results will open the way to the generation of entangled photons by current injection, analogous to current-driven single photon sources6,7.

Diffraction-interference patterns of parametric down-converted photons through a transmission grating by both one- and two-photon detection schemes are presented. The measured patterns are explained by the Fourier analysis of the two-photon wave packet, considering the quantum spatial correlation between the constituent photons. Spatial diffraction-interference patterns were recorded by a two-photon detector consisting of two avalanche photodiodes. For comparison, diffraction-interference patterns of Ti:sapphire laser are also observed using the same apparatus (a uncorrelated case).

Summary form only given. Recently, Jacobson et al. ( see Phys. Rev. Lett., vol.74, p. 4835 (1995)) proposed the concept of "photonic de Broglie wave" in multiphoton states. They argued that the photonic de Broglie wavelength of an ensemble of photons with wavelength /spl lambda//sub 0/ and average number of photons N can be measured using a special interferometer with "effective beam splitters" that do not split the multiphoton states into constituent photons. Fonseca et al. see Phys. Rev. Lett., vol. 82, p. 2868 (1999)) measured the photonic de Broglie wavelength of a two-photon state ("biphoton") using a kind of Young's interferometer. We propose and demonstrate the measurement of photonic de Broglie wavelength of biphotons generated by parametric down-conversion utilizing the usual Mach-Zehnder interferometer.

In terms of the concept of "photonic de Broglie wave" in multiphoton states, we demonstrate biphoton interference experiments using a Mach-Zehnder interferometer. We have observed interferometric oscillations corresponding to the photonic de Broglie wavelength of the biphoton.

Using a basic Mach-Zehnder interferometer, we demonstrate experimentally the measurement of the photonic de Broglie wavelength of entangled photon pairs (biphotons) generated by spontaneous parametric down-conversion. The observed interference manifests the concept of the photonic de Broglie wavelength. We also discuss the phase uncertainty obtained from the experiment.

We demonstrate one- and two-photon diffraction and interference experiments utilizing parametric down-converted photon pairs (biphotons) and a transmission grating. With two-photon detection, the biphoton exhibits a diffraction-interference pattern equivalent to that of an effective single particle that is associated with half the wavelength of the constituent photons. With one-photon detection, however no diffraction-interference pattern is observed. We show that these phenomena originate from the spatial quantum correlation between the down-converted photons., 4 pages, 5 figures

Thickness uniformities of poly-crystalline silicon thin films, deposited by a commercial LPCVD reactor, were investigated through a phenomenological and elementary reaction analysis. To understand the deposition rate and its profile in radius direction of ø 6”h silicon wafer, concentration distributions of film precursors were examined by solving basic diffusion equations of film precursors in the CVD system. The experimental thickness distribution can be simulated very well with the solution by optimizing η, the sticking probabilities of the precursors. While most of the silicon deposition was made by source precursor (mono-silane, SiH4), two kinds of intermediate species with sticking probabilities of 5X10-2 and 7X10-4 were found to contribute the deposition. Subsequently, elementary chemical reaction analysis of poly-crystalline silicon CVD process was performed using ChemKinTM and two chemical species, SiH2 and Si2H6, were identified as the possible candidates for the intermediate species.

The phylogenetic relationship of Atractylodes lancea, A. chinensis, A. koreana, A. ovata and A. japonica were analyzed by comparing the 2.6 kb sequence in a chloroplast gene trnK encoding tRNALys (UUU). The dried rhizomes of the former three species have been used as the crude drug "So-jutsu" and those of the latter two as "Byaku-jutsu" in Chinese and Japanese traditional medicine ("Kampo-medicine"). The trnK phylogenetic tree revealed that A. ovata is an outgroup of the five Atractylodes species examined and that A. japonica and A. lancea are most closely related. PCR amplification of trnK with HinfI digestion provided us with a simple method to distinguish A. ovata from other Atractylodes species at the molecular level.

To investigate muscular adaptation to swimming training in young horses, 18 two-year-old Thoroughbred horses were trained in a program which included both running and swimming, and the changes in skeletal muscle composition during the training period were evaluated histochemically. The horses were divided into the following three groups; Group A, trained by running only: Group B, trained by running plus a gradual increase in swimming; Group C, trained by running plus constant swimming. In Groups B and C, fast twitch-low oxidative (FT) fibers tended to decrease, while fast twitch-high oxidative (FTH) fibers to increase with the training progressed. The tendency was more remarkable in Group B. Therefore, in these two groups, it was suggested that the horses' aerobic capacity at the muscular level was improved significantly.

Nanolithography has been studied by using electron beam technology. Ten-nm linewidth PMMA resist patterns have been demonstrated by 50 kV scanning electron beam. The self-developing properties of a AlF3 doped LiF inorganic resist under a scanning electron beam irradiation with energy of 20–50 keV have been studied for sub-10 nm lithography. By optimizing the inorganic resist film quality, 5 nm linewidth patterns with 60 nm periodicity were directly delineated under a 30 keV electron beam. Another approach for nanolithography using electron beam holography has been proposed. Line and dot patterns with 100 nm periodicity were exposed on PMMA resist by electron beam holography with thermal field emitter gun and an electron biprism. Subsequent atomic force microscope observation has confirmed that both patterns are successfully fabricated. This technique allows us to produce nanoscale periodic patterns simultaneously. The selective atomic desorption of Cl atoms adsorbed on a Si (111) 7×7 surface has been studied by field evaporation using a scanning tunneling microscope (STM). The STM tip is placed on the adsorbed Cl on the surface, and pulse voltage was applied. This results in selective atomic desorption of Cl.

The conversion efficiency of black-dye-based dye-sensitized solar cell (DSC) was improved by cosensitization with organic dye (NKX-2553 or D131). This improved conversion efficiency was further enhanced by employing deoxycholic acid (DCA) as a coadsobent. The highest conversion efficiency, 11.6% under AM 1.5 irradiation (100 mW cm−2), was obtained in DSC with black dye and D131 in the presence of DCA.

To investigate the validity of swimming training, the following matters were considered: 1) changes in the performance capacity, 2) changes in the constitution and 3) frequency of locomotor diseases. These were evaluated during a training program including both conventional exercise on a track and swimming. In this study, 24 two-year-old thoroughbred horses were studied, and divided into the following three groups: Group A, trained by only running; Group B, trained by running plus a gradual increase in swimming; Group C, trained by running plus constant swimming. As a result of standardized exercise tests, only the intercepts of the 3 regression curves between the speed and the blood lactate concentration in Group B increased significantly as the training progressed. While the growth in height in Groups B and C were greater than in Group A, the increase in girth and weight in Groups B and C were smaller than in Group A. The percentages with locomotor diseases during this experiment in Groups A, B, and C were 62.5%, 12.5% and 25.0%, respectively, and there was a significant difference (p < 0.05) between Group A and Group B. As mentioned, it was suggested that a training program including swimming training is seen as being useful for improvement in performance capacity, since it can reduce locomotor diseases in young horses and allow for smooth progress in future training.

An 11-year-old Japanese boy with Olmsted syndrome was seen at our clinic. He had a sharply marginated, painful keratoderma with a red border on his palms and soles. Flexion contractures of the fingers were also observed. Hyperkeratotic plaques were present below the lower lip, on the elbows and knees, and in the sacral area. Localized alopecia, leukokeratosis on the tongue, shortness of stature, and laxity of the large joints corresponded to the clinical features of Olmsted syndrome. Treatment with etretinate was effective for the palms and fingers, but resulted in no improvement of the keratoderma of the soles. Because of periosteal thickening of the tibia, presumably caused by etretinate, therapy was terminated one year after it began.

This study was designed to determine the quantity of functional renal tissue needed to maintain homeostasis of red blood cell production by evaluating the erythropoietin (EPO) production response to phlebotomic stimulation in the 1/2- and 1/4-kidney dogs surgically prepared. The results showed that the reduction in functional renal tissue caused a decrease in EPO production, which led to the delay in recovery from anemia. In the anemic progress stage, the plasma EPO level showed a transition proportional to the quantity of functional renal tissue immediately after the operation for tissue reduction. The 1/2-kidney dog group still kept such proportional relation even in the recovery stage. Thus, the half of the normal renal tissue was considered sufficiently contributory to EPO production needed to maintain homeostasis of red blood cell production. However, the 1/4-kidney dog group precipitously decreased in plasma EPO level in the recovery stage and fell into an extremely unfavorable anemia. This indicated that homeostatic maintenance in erythropoiesis would be impossible more below a quarter of normal renal tissue. These findings disclosed that reduction in functional renal tissue quantity would sensitively influence homeostatic maintenance of red blood cell production through the decrease in EPO production, even if it does not affect renal function concerned with urine production.

We demonstrate efficient up-conversion detection of photons at 1550 nm utilizing bulk periodically-poled LiNbO3 (PPLN) and nanosecond-pulsed pumping. An internal conversion efficiency of 96% and an overall photon detection efficiency of 19% including the efficiency of a visible photon detector were achieved with a low dark count rate.

Cross-phase modulation(XPM) in a silicon wire waveguide at 1.55 μ m telecom band was studied down to ultralow light levels. In the low-power regime, we found that free-carrier dispersion as well as the optical Kerr effect contributes to the XPM. Possible mechanisms of the low-power XPM are discussed.

We report the high-flux and broadband generation of biphotons with controlled frequency entanglement. For the generation of the entangled state consisting of frequency-anticorrelated photons, we use PPMgSLT pumped by a continuous-wave (cw) laser. Meanwhile, the state consisting of frequency-correlated photons is produced from PPKTP under the extended phase-matching condition. Both states exhibited interference patterns with over 90% visibilities in two-photon interference experiments.

Poly-silicon deposition rate profiles on silicon wafers in several temperatures around 873 K along axial direction in commercial low-pressure chemical vapor deposition (LPCVD) reactor were investigated by both experiments and numerical simulations considering coupled computational fluid dynamics (CFD) and chemical reactions. While the chemical reaction processes of poly-silicon film deposition is a complicated system with a huge number of elementary reactions, we could successfully simulate the experimental results with a simplified 2-step surface reaction model of SiH4. Simulated film deposition rate profiles along the axial direction of reactor were in good agreement with experimental results, and the 2-step reaction model was proved to be a good tool for the numerical simulation of poly-silicon deposition process in commercial reactor.

The up-conversion dynamics of two photons in a three-level system is investigated theoretically. The analysis is based on a rigorous formalism that incorporates the multimode nature of the photon field, enabling quantitative handling of the spatial profiles of the photon pulses. We have derived an analytic formula that connects the wavefunction of two input photons to that of an up-converted output photon. The up-conversion efficiency and the output pulse profile are numerically calculated using this formula.

We have developed a high-efficiency source of cross-polarized photon pairs generated via type-II spontaneous parametric down-conversion using periodically poled lithium niobate (PPLN). The photon pairs are generated from bulk PPLN under third-order quasi-phase-matched conditions around 800 nm. We achieved a photon-pair production rate of N=1.95×106 s-1mW-1.

We propose an apparatus that realizes direct observation of nonlinear phase shifts induced by cross-phase modulation. The apparatus is based on a polarization-division Sagnac interferometer incorporating Faraday rotators, which, in principle, enables phase robustness, flexibility, and lossless operation. Here, we present the measurement of nonlinear phase shifts in a photonic crystal fiber, demonstrating the advantage of our system in its application to waveguide-type Kerr media. This apparatus is applicable to lossless all-optical phase gates and switches.

Theoretical optimization of a polysilicon low-pressure chemical vapor deposition process in a commercial scale reactor for 6 in. wafers was achieved by extracting a predictive reaction model from wafer-radial and reactor-axial deposition rate distributions. The extraction involved the radial deposition rate profile on the wafer, axial deposition rate profile in the reactor, and wafer-spacing dependence of the deposition rate at the wafer center. The deduced reaction model contains two film precursors as well as SiH 4· Based on the radial deposition rate profile, the respective sticking probabilities of these two precursors were 5 X 10 -2 and 7 X 10 -4 at 550°C. Because the two precursors could not reach the wafer center due to their high sticking probabilities, as evidenced by the low deposition rate at the wafer center, the sticking probability of SiH 4 was 1.7 X 10 -6 at 550°C with an activation energy of 161 kJ/mol. The elementary reaction simulation done here included the mass transport and the gas-phase and surface elementary reactions in the reactor. Comparison between this simulation and the experimental analysis revealed that the two film precursors probably were SiH 2 and Si2H 6 .

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We have studied shape transformation of micron-sized trenches on Si substrates during high temperature hydrogen annealing, performing numerical simulations based on Mullins' theory. We have considered evaporation-condensation and surface diffusion as mass transport mechanisms causing shape transformation. The simulation allowing only surface diffusion reproduces well the observed micron-scale aspects of shape transformation by hydrogen annealing at 1000–1150°C.

The preventive effects of recombinant human erythropoietin (rhEPO) administration on progression of anemia were evaluated during hemodialysis in nephrectomized dogs. In control dogs given no rhEPO, anemia gradually progressed with repeated hemodialysis and with little erythropoietic response observed in the bone marrow. In dogs administered with rhEPO, however, an active erythropoietic response was induced in the bone marrow, indicating that anemia due to hemodialysis was being prevented.