Frequency Measurement System of Optical Clocks Without a Flywheel Oscillator.

We developed a system for the remote frequency comparison of optical clocks. The system does not require a flywheel oscillator at the remote end, making it possible to evaluate optical frequencies even in laboratories, where no stable microwave reference, such as an Rb clock, a Cs clock, or a hydrogen maser exists. The system is established by the integration of several systems: a portable carrier-phase two-way satellite frequency transfer station and a microwave signal generation system by an optical frequency comb from an optical clock.

Measuring the charge density of a tapered optical fiber using trapped microparticles.

We report the measurements of charge density of tapered optical fibers using charged particles confined in a linear Paul trap at ambient pressure. A tapered optical fiber is placed across the trap axis at a right angle, and polystyrene microparticles are trapped along the trap axis. The distance between the equilibrium position of a positively charged particle and the tapered fiber is used to estimate the amount of charge per unit length of the fiber without knowing the amount of charge of the trapped particle.

Hong-Ou-Mandel interference of two phonons in trapped ions.

The quantum statistics of bosons and fermions manifest themselves in the manner in which two indistinguishable particles interfere quantum mechanically. When two photons, which are bosonic particles, enter a beam-splitter with one photon in each input port, they bunch together at either of the two output ports. The corresponding disappearance of the coincidence count is the Hong-Ou-Mandel effect.

Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.

Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap.

Experimental realization of a quantum phase transition of polaritonic excitations.

We report an experimental realization of the Jaynes-Cummings-Hubbard model using the internal and radial phonon states of two trapped ions. An adiabatic transfer corresponding to a quantum phase transition from a localized insulator ground state to a delocalized superfluid (SF) ground state is demonstrated. The SF phase of polaritonic excitations characteristic of the interconnected Jaynes-Cummings (JC) system is experimentally explored, where a polaritonic excitation refers to a combination of an atomic excitation and a phonon interchanged via a JC coupling.

Generation of Dicke states with phonon-mediated multilevel stimulated Raman adiabatic passage.

We generate half-excited symmetric Dicke states of two and four ions. We use multilevel stimulated Raman adiabatic passage whose intermediate states are phonon Fock states. This process corresponds to the spin squeezing operation and half-excited Dicke states are generated during multilevel stimulated Raman adiabatic passage.

Generation of a decoherence-free entangled state using a radio-frequency dressed state.

We propose the generation of entangled states with trapped calcium ions using a combination of an rf dressed state and a spin-dependent force. By using this method, a decoherence-free entangled state of rf qubits can be directly generated, and ideally its fidelity is close to unity. We demonstrate an rf entangled state with a fidelity of 0.

Molecular characterization of MHC class I and beta-2 microglobulin in a clonal strain of ginbuna crucian carp, Carassius auratus langsdorfii.

Clonal ginbuna crucian carp is, a naturally gynogenetic fish, and is a useful model animal for studying T-cell-mediated immunity. To gain molecular information on MHC class I molecules from this species, we have identified four types of MHC class I (caauUA-S3n, caauUF-S3n, caauZE-S3n, and caauZB-S3n) and five beta 2-microglobulin (β(2)m) (caauβ2m-1a, caauβ2m-1b, caauβ2m-2, caauβ2m-3a and caauβ2m-3b) by an expressed sequence tag (EST) analysis and using homology cloning with degenerated primers. Like UA class I genes in other cyprinid fish, the caauUA-S3n shows features of classical MHC class I, such as conservation of all key amino acids interacting with antigenic peptides, and ubiquitous tissue expression.

Acceleration effect of sulfate ion on the dissolution of amorphous silica.

The dissolution rate of amorphous silica is enhanced by sulfate ions. The zeta potential for silica particles in Na(2)SO(4) solution was lower than that in NaCl solution with the same ionic strength. These facts indicate that the specific adsorption of sulfate ions occurred by overcoming repulsion between negative charges of the SO(4)(2-) ion and SiO(-) on the surface of silica.

Thin-cell sub-Doppler spectroscopy by spatially separated beam method and pump-probe method.

We experimentally demonstrate two methods that improve the resolution of sub-Doppler spectroscopy using a 1 mm thick vapor cell. The linewidths of the observed spectra are approximately 1 order of magnitude narrower than the Doppler width. The first method involves using a 1 mm thick cell filled with Rb atomic vapor and two spatially separated laser beams.

Phase-locked laser system for a metastable states qubit in 40 Ca+.

We describe the development of a phase-locked laser system tailored to an ion-trap-based quantum information processor with (40)Ca(+). Laser outputs from an extended cavity diode laser and a Ti:sapphire laser with output laser wavelengths of approximately 850 and 854 nm, respectively, were phase locked and used to excite a Raman transition between the D(3/2) and D(5/2) metastable states qubit. Development and the performance of the laser system are described.

Sideband-resolved spectroscopy on the 4 2S(1/2)-3 2D(5/2) transition in single calcium ions by use of fundamental waves of diode lasers.

The 4 2S(1/2)-3 2D(5/2) electric quadrupole transition in calcium ions, which is expected to be used in calcium-ion optical frequency standards, is spectroscopically investigated with a laser system that uses only fundamental waves of diode lasers as light sources. Four Zeeman components allowed by the selection rules for the electric quadrupole transition are identified. As for one Zeeman component, one large carrier and accompanying smaller first sidebands are observed, which implies that Lamb-Dicke confinement of the ion is achieved.