Storage and retrieval of a squeezed vacuum

Storage and retrieval of a squeezed vacuum was successfully demonstrated using electromagnetically induced transparency. The squeezed vacuum pulse having a temporal width of 930 ns was incident on the laser cooled 87Rb atoms with an intense control light in a coherent state. When the squeezed vacuum pulse was slowed and spatially compressed in the cold atoms, the control light was switched off. After 3 mus of storage, the control light was switched on again, and the squeezed vacuum was retrieved, as was confirmed using the time-domain homodyne method.     

Control of light pulse propagation with only a few cold atoms in a high-finesse microcavity

Propagation of a light pulse through a high-Q optical microcavity containing a few cold atoms (N<10) in its cavity mode is investigated experimentally. With less than ten cold rubidium atoms launched into an optical microcavity, up to 170 ns propagation lead time ("superluminal"), and 440 ns propagation delay time (subluminal) are observed. Comparison of the experimental data with numerical simulations as well as future experiments are discussed.     

Cu NMR/NQR Studies on Magnetism in Impurity/Hole-Doped Spin-Ladder Compounds

Cu nuclear magnetic resonance (NMR) spectra of impurities (Zn, Ni, and La)-doped spin-1/2 Heisenberg ladder compounds SrCu₂O₃ (Sr123) are broadened with Curie-like temperature (T) dependence. The spectra have been successfully fit by using a quasi-one-dimensional (Q1D) staggered polarization (SP) model. Such a SP has also revealed in Cu NMR measurements of Sr_14–x Ca _x Cu₂₄O₄₁ (Cax) with hole-doped ladders. The origin of possible 3D antiferromagnetic (AF) long-range ordering in (Zn and Ni)-doped Sr123 and Cax around x=12 at low T is considered to be similar. Once unpaired spins S ₀'s are induced and 3D interlayer interaction occurs, the localized spins couple in the whole system.     

Application of Automatic Chromatic Dispersion Compensation for Realization of All-Optical Network

We have studied the algorithm for the automatic chromatic dispersion compensation using bit error rate (BER) and Q-factor optimization for realization of dynamically reconfigurable all-optical network. We have made sure good performance using the compensation system by laboratory experiments.     

Generation of a squeezed vacuum resonant on a rubidium D1 line with periodically poled KTiOPO4

We report the generation of a continuous-wave squeezed vacuum resonant on the Rb D1 line (795 nm) using periodically poled KTiOPO4 (PPKTP) crystals. With a frequency doubler and an optical parametric oscillator based on PPKTP crystals, we observed a squeezing level of -2.75+/-0.14 dB and an antisqueezing level of +7.00+/-0.13 dB. This system could be utilized for demonstrating storage and retrieval of the squeezed vacuum, which is important for the ultraprecise measurement of atomic spins as well as quantum information processing.     

Separation of zeros for source signature identification under reverberant path conditions

This paper presents an approach to distinguishing the zeros representing a sound source from those representing the transfer function on the basis of Lyon's residue-sign model. In machinery noise diagnostics, the source signature must be separated from observation records under reverberant path conditions. In numerical examples and an experimental piano-string vibration analysis, the modal responses could be synthesized by using clustered line-spectrum modeling. The modeling error represented the source signature subject to the source characteristics being given by a finite impulse response. The modeling error can be interpreted as a remainder function necessary for the zeros representing the source signature.     

Combustion behaviors of isolated n-decane and ethanol droplets in carbon dioxide-rich ambience under microgravity

The burning and sooting behaviors of isolated fuel droplets for ethanol and n-decane are examined in high concentration of the ambient carbon dioxide under microgravity. A quartz fiber with the diameter of 50 μm maintains the droplet in the center of the combustion chamber and the range in the initial droplet diameter is from 0.30 to 0.80 mm. The ambience consists of oxygen, nitrogen and carbon dioxide. The concentration of oxygen is 21% in volume, and that of carbon dioxide is varied from 0% to 60% in volume. Detail measurements of the projected image of the droplet are conducted by using a high speed video camera and the effective droplet diameter squared are calculated from the surface area of the rotating body of the projected object. From evolutions of the droplet diameter squared, the instantaneous burning rates are calculated. Time history of the instantaneous burning rate clearly represents the droplet combustion events, such as the initial thermal expansion, ignition and following combustion. The instantaneous burning rate for n-decane shows an increasing trend during combustion, while that for non-sooting ethanol remains almost constant or shows a decreasing trend. A slight stepwise increase in the instantaneous burning rate is observed for larger n-decane droplets in air, which may be attributed to soot accumulation. However, this behavior of the burning rate disappears in higher concentration of carbon dioxide. Direct observation of the droplet flame indicates suppression of soot production in higher concentration of carbon dioxide and the suppression is enhanced for smaller droplet.     

Acoustic characteristics of Ni–Nb–Zr–H glassy alloys by ultrasonic shear waves

The propagation characteristics of shear horizontally polarized (SH) waves passing through (Ni₄₂Nb₂₈Zr₃₀)_100–x H_x (x = 0–15.2) glassy alloys were investigated as a function of hydrogen content. With an increase in hydrogen content, the propagation time and main frequency of the receiving waves show increase and decrease, respectively, indicating expan‐ sion in average atomic distance which comes from solution of hydrogen. In sharp contrast to crystalline alloys, the decrease in damping ratio and the delay in phase with increasing hydrogen suggest a strong settlement of hydrogen into four‐coordination sites surrounded tetrahedrally by four Zr atoms and the resulting increase in dynamic elasticity, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low temperature dependence of elastic moduli and internal friction for the glassy alloy Zr55Cu30Al10Ni5

Longitudinal and transverse wave velocities, eight kinds of elastic parameters, and dilational and shear internal frictions of Zr₅₅Cu₃₀Al₁₀Ni₅ glassy alloy were simultaneously measured as a function of temperature in the range from 77 to 373 K, using an ultrasonic pulse method. The inflections at around 150 K for wave velocities, anisotropy factor and Poisson's ratio, and the 150 K peak of shear friction seem to correspond to one topological change (pseudo‐transition) associated with an interatomic readjustment or vacancy rearrangements. The behaviors from 77 to 125 K and 125 to 373 K are due to thermal relaxation of squeezed free volumes and entropy elasticity associated with vibrational motions of clusters, respectively, accompanied by an increase in atomic distance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)