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Dive into the research topics where Yujiro Eto is active.

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Featured researches published by Yujiro Eto.


Optics Express | 2008

Observation of quadrature squeezing in a χ (2) nonlinear waveguide using a temporally shaped local oscillator pulse

Yujiro Eto; Takashi Tajima; Takuya Hirano

We report on the generation of quadrature squeezed light at 1.535 microm via single-pass optical parametric amplification in a periodically poled MgO:LiNbO(3) waveguide, and detection with a temporally shaped local oscillator. Squeezing of -4.1 dB was directly measured using the shaped local oscillator. Classical parametric gain of the shaped pulse was also investigated; a deamplification gain of -12.1 dB was observed with the amplification gain of only +13.8 dB. We experimentally show that the use of shaped pulse as local oscillator in homodyne detection allows us efficient squeezing detection with near-unit mode-matching efficiency.


Nature Photonics | 2013

Quantum tele-amplification with a continuous-variable superposition state

Jonas S. Neergaard-Nielsen; Yujiro Eto; Chang-Woo Lee; Hyunseok Jeong; Masahide Sasaki

A quantum ‘tele-amplification’ scheme that combines teleportation and the noiseless amplification of a coherent state is demonstrated by using Schrodinger-cat states prepared by photon subtraction from squeezed vacuum as an entanglement resource. This scheme can realize high-capacity communication, thus beating the homodyne limit of optical communications.


Physical Review Letters | 2011

Projective Measurement of a Single Nuclear Spin Qubit by Using Two-Mode Cavity QED

Yujiro Eto; Atsushi Noguchi; Peng Zhang; Masahito Ueda; Mikio Kozuma

We report the implementation of projective measurement on a single 1/2 nuclear spin of the (171)Yb atom by measuring the polarization of cavity-enhanced fluorescence. To obtain cavity-enhanced fluorescence having a nuclear-spin-dependent polarization, we construct a two-mode cavity QED system, in which two cyclic transitions are independently coupled to each of the orthogonally polarized cavity modes, by manipulating the energy level of (171)Yb. This system can associate the nuclear spin degrees of freedom with the polarization of photons, which will facilitate the development of hybrid quantum systems.


Optics Letters | 2007

Observation of squeezed light at 1.535 μm using a pulsed homodyne detector

Yujiro Eto; Takashi Tajima; Takuya Hirano

Squeezed light was generated at a telecommunication wavelength via single-pass optical parametric amplification in a periodically poled MgO-dopedLiNbO3 waveguide. Classical parametric deamplification of −8.9dB was achieved. This large magnitude of deamplification indicates that the problem of gain-induced diffraction was avoided by employing the waveguide. Squeezing of 3.2dB was directly observed using a time-domain pulsed homodyne detector.


Physical Review A | 2013

Spin-echo-based magnetometry with spinor Bose-Einstein condensates

Yujiro Eto; Hayato Ikeda; Hirosuke Suzuki; Sho Hasegawa; Yasushi Tomiyama; Sawako Sekine; Mark Sadgrove; Takuya Hirano

We demonstrate detection of a weak alternate-current magnetic field by application of the spin echo technique to F = 2 Bose-Einstein condensates. A magnetic field sensitivity of 12 pT/Hz^1/2 is attained with the atom number of 5*10^3 at spatial resolution of 99 \mu m^2. Our observations indicate magnetic field fluctuations synchronous with the power supply line frequency. We show that this noise is greatly suppressed by application of a reverse phase magnetic field. Our technique is useful in order to create a stable magnetic field environment, which is an important requirement for atomic experiments which require a weak bias magnetic field.


Optics Letters | 2011

Efficient homodyne measurement of picosecond squeezed pulses with pulse shaping technique

Yujiro Eto; Akane Koshio; Akito Ohshiro; Junichi Sakurai; Keiko Horie; Takuya Hirano; Masahide Sasaki

We report on the detection of picosecond pulsed squeezed light generated by an optical parametric amplification in a periodically poled MgO:LiNbO(3) waveguide. By using a temporally shaped local oscillator in a balanced homodyne detection, we obverved the squeezing of -5.0 dB below the shot noise level. The squeezing level at the exit of the waveguide was estimated to be -9.7±0.8 dB.


Japanese Journal of Applied Physics | 2006

Pulsed homodyne detection of squeezed light at telecommunication wavelength

Yujiro Eto; Takashi Tajima; Takuya Hirano

We present the generation of pulsed squeezed light at telecommunication wavelength of 1.535 µm via single-pass parametric amplification in a periodically poled MgO-doped lithium niobate waveguide using a novel collinear configuration. The quadrature-amplitude of squeezed light is measured in time domain. The classical parametric deamplification of -3.2 dB and quadrature squeezing of -1.5 dB are observed. The maximum classical parametric amplification of 19.3 dB is obtained at pump average power of 0.47 mW, taking advantage of the tight confinement in a waveguide and high peak power of the pulsed light.


Scientific Reports | 2015

Experimental realization of spatially separated entanglement with continuous variables using laser pulse trains.

Ryuhi Okubo; Mayumi Hirano; Yujiro Eto; Takuya Hirano

Spatially separated entanglement is demonstrated by interfering two high-repetition squeezed pulse trains. The entanglement correlation of the quadrature amplitudes between individual pulses is interrogated. It is characterized in terms of the sufficient inseparability criterion with an optimum result of in the frequency domain and in the time domain. The quantum correlation is also observed when the two measurement stations are separated by a physical distance of 4.5 m, which is sufficiently large to demonstrate the space-like separation, after accounting for the measurement time.


Scientific Reports | 2015

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength

Kentaro Wakui; Yujiro Eto; Hugo Benichi; Shuro Izumi; Tetsufumi Yanagida; Kazuhiro Ema; Takayuki Numata; Daiji Fukuda; Masahiro Takeoka; Masahide Sasaki

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshkos criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology.


Journal of the Physical Society of Japan | 2013

Ramsey interferometry using the Zeeman sublevels in a spin-2 Bose gas

Mark Sadgrove; Yujiro Eto; Sawako Sekine; Hirosuke Suzuki; Takuya Hirano

We perform atom interferometry using the Zeeman sublevels of a spin-2 Bose–Einstein condensate of 87Rb. The observed fringes are strongly peaked, and fringe repetition rates higher than the fundamental Ramsey frequency are found in agreement with a simple theory based on spin rotations. With a suitable choice of initial states, the interferometer could function as a useful tool for magnetometry and studies of spinor dynamics in general.We perform atom interferometry using the Zeeman sublevels of a spin-2 Bose–Einstein condensate of 87Rb. The observed fringes are strongly peaked, and fringe repetition rates higher than the fundamental Ramsey frequency are found in agreement with a simple theory based on spin rotations. With a suitable choice of initial states, the interferometer could function as a useful tool for magnetometry and studies of spinor dynamics in general.

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Hiroki Saito

University of Electro-Communications

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Atsushi Noguchi

Tokyo Institute of Technology

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Masahide Sasaki

National Institute of Information and Communications Technology

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Masaya Kunimi

Yukawa Institute for Theoretical Physics

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Mikio Kozuma

Tokyo Institute of Technology

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Peng Zhang

Renmin University of China

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