T. Yabuzaki

Spin squeezing via one-axis twisting with coherent light.

We propose a new method of spin squeezing of atomic spin, based on the interactions between atoms and off-resonant light which are known as paramagnetic Faraday rotation and fictitious magnetic field of light. Since the projection process, squeezed light, or special interactions among the atoms are not required in this method, it can be widely applied to many systems. The attainable range of the squeezing parameter is S^{-2/5}, where S is the total spin, which is limited by additional fluctuations imposed by coherent light and the spherical nature of the spin distribution.

Injection-Locking of Blue Laser Diodes and Its Application to the Laser Cooling of Neutral Ytterbium Atoms

We present a simple, laser-diode-based ultraviolet light source with sufficient power and narrow linewidth. In this scheme, an injection-locking technique was applied, for the first time to our knowledge, to a GaN blue laser diode (LD). By injecting ~5 mW output light of the external cavity laser diode (ECLD) into two free-running blue slave LDs, we could obtain an output power of over 30 mW from the injection-locked slave LDs. The characterisitics of the injection-locked slave LD were studied in detail. We also present an absolute frequency-locking scheme with about a 500 MHz locking bandwidth, where we achieved offset-locking of the frequencies of two ECLDs. As an interesting example of the application of these developments, we demonstrated laser cooling and trapping of ytterbium atoms.

Topological creation of a multiply charged quantized vortex in the Rb Bose-Einstein condensate

A quadruply-charged quantized vortex has been created successfully in the 87Rb Bose-Einstein Condensate (BEC). The condensate was confined in a cloverleaf magnetic trap, and the vortex was formed by the reversal of the axial magnetic field. The vortex could be observed only in a holding time of about 1 ms, which was much shorter than that reported in the Na BEC, and the vortex position was also unstable in the BEC. To overcome these experimental difficulties, we took the following two measures and improved the vortex formation: (i) axial confinement with a FORT, which prevents the BEC from axial expansion after the field reversal, and (ii) compensation of gravity with a blue-detuned laser beam, which removes the gravitational sag.

Fast polarimetry system for the application to spin quantum non-demolition measurement

We report the development of a fast pulse polarimeter for the application to quantum non-demolition measurement of atomic spin (spin QND). The developed system was tunable to the atomic resonance of a ytterbium atom and has narrow laser line width suitable for spin QND. Using the developed polarimeter, we successfully demonstrated the measurement of the vacuum noise, with 106 to 107 photon number per pulse.

Paramagnetic Faraday rotation with spin-polarized ytterbium atoms

We report the observation of paramagnetic Faraday rotation of spin-polarized ytterbium (Yb) atoms. As the atomic samples, we used an atomic beam, released atoms from a magneto-optical trap (MOT), and trapped atoms in a far-off-resonant trap (FORT). Since Yb is diamagnetic and includes a spin-1/2 isotope, it is an ideal sample for spin physics, such as quantum non-demolition measurement of spin (spin QND), for example. From the results of the rotation angle, we confirmed that the atoms were almost perfectly polarized.

Generation of Bose-Einstein condensates in a well isolated low-pressure vacuum chamber

Bose–Einstein condensates of 87 Rb atoms are generated in a double-chamber configuration where for transfer of atoms between the chambers an extremely narrow tube is used, which offers good vacuum isolation between the two chambers. By performing time-of-flight absorption imaging, the condensate atom number and the temperature are determined.

Visualization of foreign atoms by optical magnetic-resonance imaging of Cs atoms

We perform optical magnetic-resonance (MR) imaging of Cs atoms that are polarized by the transfer from the polarized Xe or Rb atoms in a glass cell as well as by direct optical pumping. With MR images of Cs by alternate optical pumping and detection the distribution of polarized Xe or Rb of low gas pressure is observed in a weak magnetic field. We also discuss the effect of the spin-relaxation and the spin-exchange collisions between Cs, Xe, and Rb atoms on the spatial resolution of MR images of the diffusing Cs atoms.

Bose‐Einstein Condensation of Yb atoms

We could recently achieve the Bose Einstein condensation (BEC) of Yb atoms. Yb differs from most of the elements that have previously been condensed, because it is a two‐electron atom with the singlet S ground state. Furthermore the Bosonic isotopes of Yb, like 174Yb which we succeeded to condensate, has no nuclear spin, so that the ground state is completely spin‐less state and hence insensitive to magnetic fields. Thus a new type of atom could join the group of atoms for BEC studies. We would like to report how we could achieve the BEC of Yb atoms.

BOSE-EINSTEIN CONDENSATION OF YTTERBIUM ATOMS

We report the achievement of Bose-Einstein condensation of ytterbium (Yb) atoms by the all-optical method. The Yb atomic beam from an oven is first decelerated by the Zeeman slowing technique using the singlet transition and then captured by a magnetooptical trap using an intercombination transition. The evaporative cooling is performed in a novel crossed optical trap, which results in the formation of condensates of about 5 x 10 3 atoms of 174 Yb. We determine the scattering length of 174 Yb to be between 1 and 3 nm by combining the behavior of the condensate and the result of measuring photoassociation. The prospect of Yb condensates is also discussed.