Faculty of International Social Sciences

Kosuke Shibata

  (柴田 康介)

Profile Information

Affiliation
Faculty of Science Department of Physics, Gakushuin University
Degree
博士(理学)(京都大学)
修士(理学)(京都大学)

Researcher number
90735440
J-GLOBAL ID
201401011808942496
researchmap Member ID
7000007606

Research Interests

 1

Papers

 19
  • Junnosuke Takai, Kosuke Shibata, Naota Sekiguchi, Takuya Hirano
    Physical Review A, May 11, 2023  
  • Aki Torii, Kosuke Shibata, Yujiro Eto, Takuya Hirano
    Optics Express, 30(15) 26120-26120, Jul 18, 2022  
    We report on the waveguide-based generation of pulsed squeezed light at 795 nm, suitable for quantum enhanced measurements with rubidium atoms. Pulsed ultraviolet second harmonic light with a power of more than 400 mW is produced using a periodically poled LiNbO3 (PPLN) waveguide and is injected into another PPLN waveguide to generate quadrature squeezing. We find that the phase of the second harmonic pulse is shifted within a pulse, and we attribute the shift to heating due to blue-light induced infrared absorption (BLIIRA) from a comparison between the experiment and a numerical simulation. A squeezing level of −1.5(1) dB is observed in homodyne detection when we apply a linear phase shift to the local oscillator. The experiment and simulation imply that the squeezing level can be further improved by reducing BLIIRA.
  • Naota Sekiguchi, Kosuke Shibata, Aki Torii, Hiroyuki Toda, Ryohei Kuramoto, Daiki Fukuda, Takuya Hirano
    Physical Review A, 104(4), Oct 28, 2021  Peer-reviewedCorresponding author
  • Kosuke Shibata, Naota Sekiguchi, Takuya Hirano
    Physical Review A, 103(4), Apr 30, 2021  Peer-reviewedLead authorCorresponding author
    We demonstrate detection of a vector light shift (VLS) using the quantum lock-in method. The method offers precise VLS measurement with little affect from real magnetic field fluctuation. We detect a VLS on a Bose-Einstein condensate (BEC) of Rb87 atoms caused by an optical trap beam with a resolution less than 1 Hz. We demonstrate the elimination of a VLS by controlling the beam polarization to realize a long coherence time of an F=2 BEC in the stretched state. Quantum lock-in VLS detection should find wide application, including the study of spinor BECs, electric dipole moment searches, and precise magnetometry.
  • Kosuke Shibata, Hidehiko Ikeda, Ryota Suzuki, Takuya Hirano
    Physical Review Research, 2(1), Jan 23, 2020  Peer-reviewed
    We demonstrate gravity compensation for an ultracold gas of Rb87 atoms with a time-averaged optical potential. The position of a far-off-resonance beam is temporally modulated with an acousto-optic deflector to efficiently produce a potential with a linear gradient independent of the atomic magnetic sublevels. We realize compensation of the gravity sag and preparation of a degenerate gas in a trap with weak vertical confinement. Optical gravity compensation will provide the opportunity to perform experiments under microgravity in a laboratory and broaden the scope of cold atom research.

Major Misc.

 12
  • Kosuke Shibata, Ryuta Yamamoto, Yu Seki, Yoshiro Takahashi
    PHYSICAL REVIEW A, 89(3), Mar, 2014  
    We demonstrated high-sensitivity optical spectral imaging of a single layer of a quantum gas of ytterbium atoms in a two-dimensional optical lattice using the ultranarrow S-1(0)-P-3(2) transition. We successfully obtained a set of excitation-frequency-dependent fluorescence images with an excitation laser of the linewidth of 1 kHz (FWHM), and the overall features were well explained by considering the inhomogeneous light shift originating from the Gaussian beam shape of the optical lattice potential which provided the steepest potential gradient of 3.6 kHz/mu m. This result is also the successful demonstration of the tunable local atom addressing along the equipotential contour depending on the excitation laser frequency with the frequency resolution of 8 kHz and the spatial resolution of approximately 2 mu m. The demonstrated technique will be useful for many purposes including the measurement of interaction shift in the study of a quantum gas and quantum information processing.
  • Kosuke Shibata, Ryuta Yamamoto, Yoshiro Takahashi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 83(1), Jan, 2014  
    We developed a dual molasses technique which enabled us to perform high-sensitivity in situ fluorescence imaging of ytterbium (Yb) atoms in a two-dimensional optical lattice prepared in a thin glass cell. This technique successfully combines two different kinds of optical molasses for Yb atoms, that is, the one using the S-1(0)-P-1(1) transition which provides high-resolution in the in situ fluorescence imaging and the other using the S-1(0)-P-3(1) transition for cooling the atoms in the optical lattice. We performed in situ imaging of Yb-174 atoms and could observe a Moire pattern with a period of about 6 mu m produced by the molasses beam with 556 nm and the optical lattice with 532 nm, which implies that the temperature was kept below the lattice depth during the fluorescence imaging. The number of photons per atom is estimated to be enough for single atom detection with our imaging system. This result is quite promising for the realization of an Yb quantum gas microscope.

Presentations

 16

Research Projects

 6