T. Takagahara

Kyoto Institute of Technology

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Eiichi Hanamura

The University of Tokyo

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Özgür Çakır

Izmir Institute of Technology

Selvakumar V. Nair

University of Toronto

Masami Kumagai

NTT Basic Research Laboratories

Ryogo Kubo

Keio University

Jiro Temmyo

Shizuoka University

Hideki Gotoh

NTT Basic Research Laboratories

Chih‐Kang Shih

The University of Texas at Austin

Han Htoon

Los Alamos National Laboratory

Takeyoshi Sugaya

National Institute of Advanced Industrial Science and Technology

Cooperative Institutions

Japan Science and Technology Agency

NTT Basic Research Laboratories

The University of Tokyo

Tohoku University

National Institute of Advanced Industrial Science and Technology

NTT (Japan)

NTT (United States)

RIKEN

Osaka University

Kyoto University

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Exciton Rabi Oscillation in Single Isolated Quantum Dots

physica status solidi (a) (2002)

H. Kamada Hideki Gotoh Jiro Temmyo Hiroaki Ando T. Takagahara

The Rabi population oscillation of a single excitonic two-level system in an isolated InxGa1—xAs quantum dot was examined by quantum wave function interferometry in the time domain. The corresponding energy splitting was also confirmed in an energy-domain measurement. Two-pulse dipole interference on an excited excitonic state revealed a long-lived coherence of zero-dimensional excitonic states and demonstrated coherent population flopping under a strong optical field.

Rabi cycle

Rabi frequency

Oscillation (cell signaling)

10.1002/1521-396x(200204)190:2<485::aid-pssa485>3.0.co;2-4

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Citations (7)

Quantum coherence phenomena in semiconductor quantum dots: quantum interference, decoherence and Rabi oscillation

Chaos Solitons & Fractals (2002)

Han Htoon Chih‐Kang Shih T. Takagahara

Dephasing

Rabi cycle

Oscillation (cell signaling)

Rabi frequency

Quantum beats

10.1016/s0960-0779(02)00305-3

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Citations (3)

21aTA-11 Quantum Dynamics of Electron-Nuclei Coupled System in Quantum Dots

日本物理学会講演概要集 (2007)

Özgür Çakır T. Takagahara

Dynamics

Source

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A quantum device interfacing photons and spins for quantum repeaters

AIP conference proceedings (2007)

Hideo Kosaka T. Kutsuwa K. Arai Yoshiaki Rikitake K. Ôno

We present experimental and theoretical approach for building a quantum repeater. Device structure for quantum state transfer from a photon to an electron spin was designed, fabricated and evaluated. Light‐hole exciton excitation in GaAs/AlGaAs‐quantum well with near‐zero electron g‐factor showed “negative polarization”, which indicates polarization transfer from a photon to an electron spin. We have also observed dynamic nuclear polarization implying polarization transfer from a photon to a nuclear spin intermediated by an electron spin.

10.1063/1.2730280

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Non-Markoffian Theory of Electron Spin Decoherence in a Single Quantum Dot

AIP conference proceedings (2007)

T. Takagahara

We investigate theoretically the electron spin relaxation and decoherence rates in a single quantum disk and clarify their dependence on the magnetic field strength, the temperature and the strength of quantum confinement. In the weak confinement regime, the spin relaxation rate at low temperatures is dominated by the two‐phonon processes and its dependence on the magnetic field is rather weak. In the strong confinement regime, on the other hand, the spin relaxation rate at low temperatures is governed by the one‐phonon processes and exhibits the characteristic B4 dependence on the magnetic field(B). Non‐Markoffian theory is developed for the electron spin decoherence rate due to the electron‐phonon interactions based on the double Feynman diagrams. The dependencies of the electron spin decoherence rate on the magnetic field and the temperature are clarified.

10.1063/1.2730395

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Near-Field Optical Mapping of Exciton Wave Functions in a GaAs Quantum Dot

Physical Review Letters (2003)

Kazunari Matsuda Toshiharu Saiki Shin‐ichiro M. Nomura M. Mihara Y. Aoyagi

Near-field photoluminescence imaging spectroscopy of naturally occurring GaAs quantum dots (QDs) is presented. We successfully mapped out center-of -mass wave functions of an exciton confined in a GaAs QD in real space due to the enhancement of spatial resolution up to 30 nm. As a consequence, we discovered that the spatial profile of the exciton emission, which reflects the shape of a monolayer-high island, differs from that of biexciton emission, due to different distributions of the polarization field for the exciton and biexciton recombinations. This novel technique can be extensively applied to wave function engineering in the design and the fabrication of quantum devices.

Biexciton

10.1103/physrevlett.91.177401

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Citations (157)

Optical Dephasing of Excitonic Polaritons in CuCl Studied by Time-Resolved, Nondegenerate Four-Wave Mixing

Physical Review Letters (1983)

Yasuaki Masumoto Shigeo Shionoya T. Takagahara

Optical dephasing of excitonic polaritons in CuCl is directly measured for the first time in the picosecond time domain by means of time-resolved, nondegenerate four-wave mixing. Dephasing of the ${\ensuremath{\omega}}_{1}$ polariton pulse is probed by an interrogation ${\ensuremath{\omega}}_{2}$ polariton pulse whose group velocity is faster than that of the ${\ensuremath{\omega}}_{1}$ polariton pulse. It is found that the dephasing damping constant $\frac{\ensuremath{\Gamma}}{2}$ of excitonic polaritons is of order of 0.01 meV and increases as $\ensuremath{\hbar}{\ensuremath{\omega}}_{1}$ approaches the exciton resonance energy from below.

Dephasing

Picosecond

Four-wave mixing

10.1103/physrevlett.51.923

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Citations (80)

Theory Of Many Exciton States And Biexciton Iasing In Semiconductor Nanocrystals

T. Takagahara Selvakumar V. Nair

Biexciton

10.1109/cleopr.1997.610462

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Electron—phonon interactions in semiconductor nanocrystals

Journal of Luminescence (1996)

T. Takagahara

Dephasing

10.1016/0022-2313(96)00050-6

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Citations (178)

Physical review. B, Condensed matter (1996)

Selvakumar V. Nair T. Takagahara

We present a calculation of the two-exciton states in semiconductor quantum dots much larger in size than the exciton Bohr radius, and identify a weakly correlated exciton pair state that has a large oscillator strength, increasing proportionately to the volume of the quantum dot. This state is shown to be responsible for the saturation of the size dependence of the resonant excitonic optical nonlinearity. It also provides a satisfactory understanding of the blueshift of the excited-state absorption in quantum dots. These results and the biexciton binding energy and oscillator strength are in good agreement with reported experimental results on CuCl.

Bohr radius

Biexciton

Oscillator strength

Bohr model

Fine structure

10.1103/physrevb.53.r10516

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Citations (13)