Bio


Yamamoto's current research interests are in the areas of quantum information, quantum optics, and mesoscopic physics such as squeezed states, quantum nondemolition measurements, cavity quantum electrodynamics, quantum computers, and mesoscopic electron transport and tunneling.

Academic Appointments


Honors & Awards


  • Medal with Purple Ribbon, Emperor of Japan (2005)

Professional Education


  • PhD, Tokyo (1978)

Journal Articles


  • An electrically pumped polariton laser NATURE Schneider, C., Rahimi-Iman, A., Kim, N. Y., Fischer, J., Savenko, I. G., Amthor, M., Lermer, M., Wolf, A., Worschech, L., Kulakovskii, V. D., Shelykh, I. A., Kamp, M., Reitzenstein, S., Forchel, A., Yamamoto, Y., Hoefling, S. 2013; 497 (7449): 348-352

    Abstract

    Conventional semiconductor laser emission relies on stimulated emission of photons, which sets stringent requirements on the minimum amount of energy necessary for its operation. In comparison, exciton-polaritons in strongly coupled quantum well microcavities can undergo stimulated scattering that promises more energy-efficient generation of coherent light by 'polariton lasers'. Polariton laser operation has been demonstrated in optically pumped semiconductor microcavities at temperatures up to room temperature, and such lasers can outperform their weak-coupling counterparts in that they have a lower threshold density. Even though polariton diodes have been realized, electrically pumped polariton laser operation, which is essential for practical applications, has not been achieved until now. Here we present an electrically pumped polariton laser based on a microcavity containing multiple quantum wells. To prove polariton laser emission unambiguously, we apply a magnetic field and probe the hybrid light-matter nature of the polaritons. Our results represent an important step towards the practical implementation of polaritonic light sources and electrically injected condensates, and can be extended to room-temperature operation using wide-bandgap materials.

    View details for DOI 10.1038/nature12036

    View details for Web of Science ID 000318952000033

  • Unconditional generation of bright coherent non-Gaussian light from exciton-polariton condensates PHYSICAL REVIEW B Byrnes, T., Yamamoto, Y., van Loock, P. 2013; 87 (20)
  • Exciton-polariton condensates near the Dirac point in a triangular lattice NEW JOURNAL OF PHYSICS Kim, N. Y., Kusudo, K., Loeffler, A., Hoefling, S., Forchel, A., Yamamoto, Y. 2013; 15
  • Very strong coupling in GaAs-based optical microcavities PHYSICAL REVIEW B Zhang, H., Kim, N. Y., Yamamoto, Y., Na, N. 2013; 87 (11)
  • Commissioning of KEKB PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS Abe, T., Akai, K., Cai, Y., Ebihara, K., Egawa, K., Enomoto, A., Flanagan, J., Fukuma, H., Funakoshi, Y., Furukawa, K., Furuya, T., Haba, J., Hiramatsu, S., Hosoyama, K., Ieiri, T., Iida, N., Ikeda, H., Iwasaki, M., Kageyama, T., Kamada, S., Kamitani, T., Kato, S., Kikuchi, M., Kikutani, E., Koiso, H., Kurokawa, S., Masuzawa, M., Matsumoto, T., Mimashi, T., Miura, T., Morita, A., Morita, Y., Nakamura, T. T., Nakanishi, K., Nishiwaki, M., Ogawa, Y., Ohmi, K., Ohnishi, Y., Ohsawa, S., Ohuchi, N., Oide, K., Oki, T., Ono, M., Perevedentsev, E., Satoh, K., Satoh, M., Seimiya, Y., Shibata, K., Shimada, M., Suetake, M., Suetsugu, Y., Sugimura, T., Suwada, T., Tajima, O., Tawada, M., Tejima, M., Tobiyama, M., Tokuda, N., Uehara, S., Uno, S., Yamamoto, Y., Yano, Y., Yokoyama, K., Yoshida, M., Yoshida, M., Yoshimoto, S., Yoshioka, M., Zhou, D., Zong, Z. 2013
  • Achievements of KEKB PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS Abe, T., Akai, K., Akasaka, N., Akemoto, M., Akiyama, A., Arinaga, M., Cai, Y., Ebihara, K., Egawa, K., Enomoto, A., Ezura, E., Flanagan, J., Fukuda, S., Fukuma, H., Funakoshi, Y., Furukawa, K., Furuya, T., Haba, J., Hara, K., Higo, T., Hiramatsu, S., Hisamatsu, H., Honma, H., Honma, T., Hosoyama, K., Ieiri, T., Iida, N., Ikeda, H., Ikeda, M., Inagaki, S., Isagawa, S., Ishii, H., Kabe, A., Kadokura, E., Kageyama, T., Kakihara, K., Kako, E., Kamada, S., Kamitani, T., Kanazawa, K., Katagiri, H., Kato, S., Kawamoto, T., Kazakov, S., Kikuchi, M., Kikutani, E., Kitagawa, K., Koiso, H., Kojima, Y., Komada, I., Kubo, T., Kudo, K., Kurokawa, S., Marutsuka, K., Masuzawa, M., Matsumoto, S., Matsumoto, T., Michizono, S., Mikawa, K., Mimashi, T., Mitsuhashi, T., Mitsunobu, S., Miura, T., Mori, K., Morita, A., Morita, Y., Nakai, H., Nakajima, H., Nakamura, T. T., Nakanishi, H., Nakanishi, K., Nakao, K., Nakayama, H., Nishiwaki, M., Ogawa, Y., Ohmi, K., Ohnishi, Y., Ohsawa, S., Ohsawa, Y., Ohuchi, N., Oide, K., Oki, T., Ono, M., Ozaki, T., Perevedentsev, E., Sakai, H., Sakamoto, Y., Sato, M., Satoh, K., Satoh, M., Seimiya, Y., Shibata, K., Shidara, T., Shimada, M., Stanic, S., Shirai, M., Shirakawa, A., Sueno, T., Suetake, M., Suetsugu, Y., Sugahara, R., Sugimura, T., Suwada, T., Tajima, O., Takano, S., Takasaki, S., Takenaka, T., Takeuchi, Y., Takeuchi, Y., Tawada, M., Tejima, M., Tobiyama, M., Tokuda, N., Tsuchiya, K., Uehara, S., Uno, S., Wu, Y., Yamamoto, N., Yamamoto, Y., Yano, Y., Yokoyama, K., Yoshida, M., Yoshida, M., Yoshimoto, S., Yoshino, K., Yoshioka, M., Zhou, D., Zimmermann, F., Zong, Z. 2013
  • Photoluminescence of a microcavity quantum dot system in the quantum strong-coupling regime SCIENTIFIC REPORTS Ishida, N., Byrnes, T., Nori, F., Yamamoto, Y. 2013; 3

    Abstract

    The Jaynes-Cummings model, describing the interaction between a single two-level system and a photonic mode, has been used to describe a large variety of systems, ranging from cavity quantum electrodynamics, trapped ions, to superconducting qubits coupled to resonators. Recently there has been renewed interest in studying the quantum strong-coupling (QSC) regime, where states with photon number greater than one are excited. This regime has been recently achieved in semiconductor nanostructures, where a quantum dot is trapped in a planar microcavity. Here we study the quantum strong-coupling regime by calculating its photoluminescence (PL) properties under a pulsed excitation. We discuss the changes in the PL as the QSC regime is reached, which transitions between a peak around the cavity resonance to a doublet. We particularly examine the variations of the PL in the time domain, under regimes of short and long pulse times relative to the microcavity decay time.

    View details for DOI 10.1038/srep01180

    View details for Web of Science ID 000314396700005

    View details for PubMedID 23378913

  • Optical Pumping of a Single Electron Spin Bound to a Fluorine Donor in a ZnSe Nanostructure NANO LETTERS Sleiter, D. J., Sanaka, K., Kim, Y. M., Lischka, K., Pawlis, A., Yamamoto, Y. 2013; 13 (1): 116-120

    Abstract

    Here we demonstrate optical pumping of a single electron within a semiconductor nanostructure comprised of a single fluorine donor located within a ZnSe/ZnMgSe quantum well. Experiments were performed to detect optical pumping behavior by observing single photons emitted from the nanostructure when the electron changes spin state. These results demonstrate initialization and read-out of the electron spin qubit and open the door for coherent optical manipulation of a spin by taking advantage of an unconventional nanostructure.

    View details for DOI 10.1021/nl303663n

    View details for Web of Science ID 000313142300021

    View details for PubMedID 23215051

  • Downconversion quantum interface for a single quantum dot spin and 1550-nm single-photon channel OPTICS EXPRESS Pelc, J. S., Yu, L., De Greve, K., McMahon, P. L., Natarajan, C. M., Esfandyarpour, V., Maier, S., Schneider, C., Kamp, M., Hoefling, S., Hadfield, R. H., Forchel, A., Yamamoto, Y., Fejer, M. M. 2012; 20 (25): 27510-27519

    Abstract

    Long-distance quantum communication networks require appropriate interfaces between matter qubit-based nodes and low-loss photonic quantum channels. We implement a downconversion quantum interface, where the single photons emitted from a semiconductor quantum dot at 910 nm are downconverted to 1560 nm using a fiber-coupled periodically poled lithium niobate waveguide and a 2.2-?m pulsed pump laser. The single-photon character of the quantum dot emission is preserved during the downconversion process: we measure a cross-correlation g(2)(? = 0) = 0.17 using resonant excitation of the quantum dot. We show that the downconversion interface is fully compatible with coherent optical control of the quantum dot electron spin through the observation of Rabi oscillations in the downconverted photon counts. These results represent a critical step towards a long-distance hybrid quantum network in which subsystems operating at different wavelengths are connected through quantum frequency conversion devices and 1.5-?m quantum channels.

    View details for Web of Science ID 000314746600031

    View details for PubMedID 23262701

  • Faster quantum chemistry simulation on fault-tolerant quantum computers NEW JOURNAL OF PHYSICS Jones, N. C., Whitfield, J. D., McMahon, P. L., Yung, M., Van Meter, R., Aspuru-Guzik, A., Yamamoto, Y. 2012; 14
  • Quantum-dot spin-photon entanglement via frequency downconversion to telecom wavelength NATURE De Greve, K., Yu, L., McMahon, P. L., Pelc, J. S., Natarajan, C. M., Kim, N. Y., Abe, E., Maier, S., Schneider, C., Kamp, M., Hoefling, S., Hadfield, R. H., Forchel, A., Fejer, M. M., Yamamoto, Y. 2012; 491 (7424): 421-?

    Abstract

    Long-distance quantum teleportation and quantum repeater technologies require entanglement between a single matter quantum bit (qubit) and a telecommunications (telecom)-wavelength photonic qubit. Electron spins in III-V semiconductor quantum dots are among the matter qubits that allow for the fastest spin manipulation and photon emission, but entanglement between a single quantum-dot spin qubit and a flying (propagating) photonic qubit has yet to be demonstrated. Moreover, many quantum dots emit single photons at visible to near-infrared wavelengths, where silica fibre losses are so high that long-distance quantum communication protocols become difficult to implement. Here we demonstrate entanglement between an InAs quantum-dot electron spin qubit and a photonic qubit, by frequency downconversion of a spontaneously emitted photon from a singly charged quantum dot to a wavelength of 1,560?nanometres. The use of sub-10-picosecond pulses at a wavelength of 2.2?micrometres in the frequency downconversion process provides the necessary quantum erasure to eliminate which-path information in the photon energy. Together with previously demonstrated indistinguishable single-photon emission at high repetition rates, the present technique advances the III-V semiconductor quantum-dot spin system as a promising platform for long-distance quantum communication.

    View details for DOI 10.1038/nature11577

    View details for Web of Science ID 000311031600041

    View details for PubMedID 23151585

  • Quantum Computing vs. Coherent Computing NEW GENERATION COMPUTING Yamamoto, Y., Takata, K., Utsunomiya, S. 2012; 30 (4): 327-355
  • Entangling Single Photons from Independently Tuned Semiconductor Nanoemitters NANO LETTERS Sanaka, K., Pawlis, A., Ladd, T. D., Sleiter, L. J., Lischka, K., Yamamoto, Y. 2012; 12 (9): 4611-4616

    Abstract

    Quantum communication systems based on nanoscale semiconductor devices is challenged by inhomogeneities from device to device. We address this challenge using ZnMgSe/ZnSe quantum-well nanostructures with local laser-based heating to tune the emission of single impurity-bound exciton emitters in two separate devices. The matched emission in combination with photon bunching enables quantum interference from the devices and allows the postselection of polarization-entangled single photons. The ability to entangle single photons emitted from nanometer-sized sources separated by macroscopic distances provides an essential step for a solid-state realization of a large-scale quantum optical network. This paves the way toward measurement-based entanglement generation between remote electron spins localized at macroscopically separated fluorine impurities.

    View details for DOI 10.1021/nl301911t

    View details for Web of Science ID 000308576000032

    View details for PubMedID 22839419

  • Layered Architecture for Quantum Computing PHYSICAL REVIEW X Jones, N. C., Van Meter, R., Fowler, A. G., McMahon, P. L., Kim, J., Ladd, T. D., Yamamoto, Y. 2012; 2 (3)
  • Two-qubit geometric phase gate for quantum dot spins using cavity polariton resonance PHYSICAL REVIEW B Puri, S., Kim, N. Y., Yamamoto, Y. 2012; 85 (24)
  • Exciton-polariton condensates with flat bands in a two-dimensional kagome lattice NEW JOURNAL OF PHYSICS Masumoto, N., Kim, N. Y., Byrnes, T., Kusudo, K., Loeffler, A., Hoefling, S., Forchel, A., Yamamoto, Y. 2012; 14
  • BEC-BCS-laser crossover in Coulomb-correlated electron-hole-photon systems NEW JOURNAL OF PHYSICS Yamaguchi, M., Kamide, K., Ogawa, T., Yamamoto, Y. 2012; 14
  • Macroscopic quantum computation using Bose-Einstein condensates PHYSICAL REVIEW A Byrnes, T., Wen, K., Yamamoto, Y. 2012; 85 (4)
  • Power-law decay of the spatial correlation function in exciton-polariton condensates PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Roumpos, G., Lohse, M., Nitsche, W. H., Keeling, J., Szymanska, M. H., Littlewood, P. B., Loeffler, A., Hoefling, S., Worschech, L., Forchel, A., Yamamoto, Y. 2012; 109 (17): 6467-6472

    Abstract

    We create a large exciton-polariton condensate and employ a Michelson interferometer setup to characterize the short- and long-distance behavior of the first order spatial correlation function. Our experimental results show distinct features of both the two-dimensional and nonequilibrium characters of the condensate. We find that the gaussian short-distance decay is followed by a power-law decay at longer distances, as expected for a two-dimensional condensate. The exponent of the power law is measured in the range 0.9-1.2, larger than is possible in equilibrium. We compare the experimental results to a theoretical model to understand the features required to observe a power law and to clarify the influence of external noise on spatial coherence in nonequilibrium phase transitions. Our results indicate that Berezinskii-Kosterlitz-Thouless-like phase order survives in open-dissipative systems.

    View details for DOI 10.1073/pnas.1107970109

    View details for Web of Science ID 000303249100032

    View details for PubMedID 22496595

  • Spin dephasing of fluorine-bound electrons in ZnSe PHYSICAL REVIEW B Greilich, A., Pawlis, A., Liu, F., Yugov, O. A., Yakovlev, D. R., Lischka, K., Yamamoto, Y., Bayer, M. 2012; 85 (12)
  • Negative Bogoliubov dispersion in exciton-polariton condensates PHYSICAL REVIEW B Byrnes, T., Horikiri, T., Ishida, N., Fraser, M., Yamamoto, Y. 2012; 85 (7)
  • Cascaded frequency upconversion for high-speed single-photon detection at 1550 nm OPTICS LETTERS Pelc, J. S., Zhang, Q., Phillips, C. R., Yu, L., Yamamoto, Y., Fejer, M. M. 2012; 37 (4): 476-478

    Abstract

    We present a device for two-stage frequency upconversion of single-photon-level signals in the 1.55 ?m telecom band to the green spectral region with low excess noise, suitable for detection by low-timing-jitter silicon single-photon avalanche photodiodes (APDs). We achieve a net conversion efficiency of 87% and a system timing jitter below 70 ps FWHM, dominated by the jitter of the APD. Modifications of our device are suitable for downconversion of single photons from visible-wavelength quantum emitters into the telecom band.

    View details for Web of Science ID 000300706500011

    View details for PubMedID 22344078

  • Semiconductor qubits based on fluorine implanted ZnMgSe/ZnSe quantum-well nanostructures PHYSICAL REVIEW B Kim, Y. M., Sleiter, D., Sanaka, K., Yamamoto, Y., Meijer, J., Lischka, K., Pawlis, A. 2012; 85 (8)
  • Transient time of an Ising machine based on injection-locked laser network NEW JOURNAL OF PHYSICS Takata, K., Utsunomiya, S., Yamamoto, Y. 2012; 14
  • Simple quantum logic gate with quantum dot cavity QED systems PHYSICAL REVIEW B Ladd, T. D., Yamamoto, Y. 2011; 84 (23)
  • Accelerated optimization problem search using Bose-Einstein condensation NEW JOURNAL OF PHYSICS Byrnes, T., Yan, K., Yamamoto, Y. 2011; 13
  • Ultrafast coherent control and suppressed nuclear feedback of a single quantum dot hole qubit NATURE PHYSICS De Greve, K., McMahon, P. L., Press, D., Ladd, T. D., Bisping, D., Schneider, C., Kamp, M., Worschech, L., Hoefling, S., Forchel, A., Yamamoto, Y. 2011; 7 (11): 872-878

    View details for DOI 10.1038/NPHYS2078

    View details for Web of Science ID 000296740000016

  • Present Status and Future Prospects of Quantum Information Processing: With Special Focus on Optically Controlled Semiconductor Spins and Single-Photon Technologies JAPANESE JOURNAL OF APPLIED PHYSICS Yamamoto, Y. 2011; 50 (10)
  • Mapping of Ising models onto injection-locked laser systems OPTICS EXPRESS Utsunomiya, S., Takata, K., Yamamoto, Y. 2011; 19 (19): 18091-18108

    Abstract

    We propose a mapping protocol to implement Ising models in injection-locked laser systems. The proposed scheme is based on optical coherent feedback and can be potentially applied for large-scale Ising problems.

    View details for Web of Science ID 000294781200039

    View details for PubMedID 21935175

  • Dynamical d-wave condensation of exciton-polaritons in a two-dimensional square-lattice potential NATURE PHYSICS Kim, N. Y., Kusudo, K., Wu, C., Masumoto, N., Loeffler, A., Hoefling, S., Kumada, N., Worschech, L., Forchel, A., Yamamoto, Y. 2011; 7 (9): 681-686

    View details for DOI 10.1038/NPHYS2012

    View details for Web of Science ID 000294485400012

  • Possible origin of the nonmonotonic doping dependence of the in-plane resistivity anisotropy of Ba(Fe(1)xT(x))(2)As-2 (T = Co, Ni and Cu) PHYSICAL REVIEW B Kuo, H., Chu, J., Riggs, S. C., Yu, L., McMahon, P. L., De Greve, K., Yamamoto, Y., Analytis, J. G., Fisher, I. R. 2011; 84 (5)
  • Room Temperature Current Injection Polariton Light Emitting Diode with a Hybrid Microcavity NANO LETTERS Lu, T., Chen, J., Lin, S., Huang, S., Wang, S., Yamamoto, Y. 2011; 11 (7): 2791-2795

    Abstract

    The strong light-matter interaction within a semiconductor high-Q microcavity has been used to produce half-matter/half-light quasiparticles, exciton-polaritons. The exciton-polaritons have very small effective mass and controllable energy-momentum dispersion relation. These unique properties of polaritons provide the possibility to investigate the fundamental physics including solid-state cavity quantum electrodynamics, and dynamical Bose-Einstein condensates (BECs). Thus far the polariton BEC has been demonstrated using optical excitation. However, from a practical viewpoint, the current injection polariton devices operating at room temperature would be most desirable. Here we report the first realization of a current injection microcavity GaN exciton-polariton light emitting diode (LED) operating under room temperature. The exciton-polariton emission from the LED at photon energy 3.02 eV under strong coupling condition is confirmed through temperature-dependent and angle-resolved electroluminescence spectra.

    View details for DOI 10.1021/nl2011164

    View details for Web of Science ID 000292849400039

    View details for PubMedID 21675759

  • Single vortex-antivortex pair in an exciton-polariton condensate NATURE PHYSICS Roumpos, G., Fraser, M. D., Loeffler, A., Hoefling, S., Forchel, A., Yamamoto, Y. 2011; 7 (2): 129-133

    View details for DOI 10.1038/NPHYS1841

    View details for Web of Science ID 000286807000014

  • Inhibition of Allergic Bronchial Asthma by Thrombomodulin Is Mediated by Dendritic Cells AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Takagi, T., Taguchi, O., Toda, M., Ruiz, D. B., Bernabe, P. G., D'Alessandro-Gabazza, C. N., Miyake, Y., Kobayashi, T., Aoki, S., Chiba, F., Yano, Y., Conway, E. M., Munesue, S., Yamamoto, Y., Yamamoto, H., Suzuki, K., Takei, Y., Morser, J., Gabazza, E. C. 2011; 183 (1): 31-42

    Abstract

    bronchial asthma is caused by inappropriate acquired immune responses to environmental allergens. It is a major health problem, with a prevalence that is rapidly increasing. Curative therapy is not currently available.to test the hypothesis that thrombomodulin (TM) inhibits allergic bronchial asthma by inducing tolerogenic dendritic cells (DCs).the protective effect of TM was evaluated using a murine asthma model. Asthma was induced in mice by exposure to chicken egg ovalbumin, and the effects of inhaled TM or TM-treated DCs were assessed by administering before ovalbumin exposure.treatment with TM protects against bronchial asthma measured as improved lung function and reduced IgE and cells in alveolar lavage fluid by inducing tolerogenic dendritic dells. These are characterized by high expression of surface TM (CD141/TM(+)) and low expression of maturation markers and possess reduced T-cell costimulatory activity. The CD141/TM(+) DCs migrate less toward chemokines, and after TM treatment there are fewer DCs in the draining lymph node and more in the lungs. The TM effect is independent of its role in coagulation. Rather, it is mediated via the TM lectin domain directly interacting with the DCs.the results of this study show that TM is a modulator of DC immunostimulatory properties and a novel candidate drug for the prevention of bronchial asthma in atopic patients.

    View details for DOI 10.1164/rccm.201001-0107OC

    View details for Web of Science ID 000286155600008

    View details for PubMedID 20709825

  • Photon antibunching and magnetospectroscopy of a single fluorine donor in ZnSe APPLIED PHYSICS LETTERS De Greve, K., Clark, S. M., Sleiter, D., Sanaka, K., Ladd, T. D., Panfilova, M., Pawlis, A., Lischka, K., Yamamoto, Y. 2010; 97 (24)

    View details for DOI 10.1063/1.3525579

    View details for Web of Science ID 000285481000025

  • Massive parallel generation of indistinguishable single photons via the polaritonic superfluid to Mott-insulator quantum phase transition NEW JOURNAL OF PHYSICS Na, N., Yamamoto, Y. 2010; 12
  • BCS Wave-Function Approach to the BEC-BCS Crossover of Exciton-Polariton Condensates PHYSICAL REVIEW LETTERS Byrnes, T., Horikiri, T., Ishida, N., Yamamoto, Y. 2010; 105 (18)

    Abstract

    The crossover between low and high density regimes of exciton-polariton condensates is examined using a BCS wave-function approach. Our approach is an extension of the BEC-BCS crossover theory for excitons, but includes a cavity photon field. The approach can describe both the low density limit, where the system can be described as a Bose-Einstein condensate (BEC) of exciton-polaritons, and the high density limit, where the system enters a photon-dominated regime. In contrast to the exciton BEC-BCS crossover where the system approaches an electron-hole plasma, the polariton high density limit has strongly correlated electron-hole pairs. At intermediate densities, there is a regime with BCS-like properties, with a peak at nonzero momentum of the singlet pair function. We calculate the expected photoluminescence and give several experimental signatures of the crossover.

    View details for DOI 10.1103/PhysRevLett.105.186402

    View details for Web of Science ID 000283492000007

    View details for PubMedID 21231119

  • Quantum Hall charge sensor for single-donor nuclear spin detection in silicon NEW JOURNAL OF PHYSICS Sleiter, D., Kim, N. Y., Nozawa, K., Ladd, T. D., Thewalt, M. L., Yamamoto, Y. 2010; 12
  • Pulsed Nuclear Pumping and Spin Diffusion in a Single Charged Quantum Dot PHYSICAL REVIEW LETTERS Ladd, T. D., Press, D., De Greve, K., McMahon, P. L., Friess, B., Schneider, C., Kamp, M., Hoefling, S., Forchel, A., Yamamoto, Y. 2010; 105 (10)

    Abstract

    We report the observation of a feedback process between the nuclear spins in a single charged quantum dot under coherently pulsed optical excitation and its trion transition. The optical pulse sequence intersperses resonant narrow-band pumping for spin initialization with off-resonant ultrafast pulses for coherent electron-spin rotation. A hysteretic sawtooth pattern in the free-induction decay of the single electron spin is observed; a mathematical model indicates a competition between optical nuclear pumping and nuclear spin-diffusion. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations.

    View details for DOI 10.1103/PhysRevLett.105.107401

    View details for Web of Science ID 000281486900011

    View details for PubMedID 20867546

  • In-Plane Resistivity Anisotropy in an Underdoped Iron Arsenide Superconductor SCIENCE Chu, J., Analytis, J. G., De Greve, K., McMahon, P. L., Islam, Z., Yamamoto, Y., Fisher, I. R. 2010; 329 (5993): 824-826

    Abstract

    High-temperature superconductivity often emerges in the proximity of a symmetry-breaking ground state. For superconducting iron arsenides, in addition to the antiferromagnetic ground state, a small structural distortion breaks the crystal's C(4 )rotational symmetry in the underdoped part of the phase diagram. We reveal that the representative iron arsenide Ba(Fe(1)(-x)Co(x))(2)As(2) develops a large electronic anisotropy at this transition via measurements of the in-plane resistivity of detwinned single crystals, with the resistivity along the shorter b axis rho(b) being greater than rho(a). The anisotropy reaches a maximum value of ~2 for compositions in the neighborhood of the beginning of the superconducting dome. For temperatures well above the structural transition, uniaxial stress induces a resistivity anisotropy, indicating a substantial nematic susceptibility.

    View details for DOI 10.1126/science.1190482

    View details for Web of Science ID 000280809900046

    View details for PubMedID 20705856

  • In-plane electronic anisotropy in underdoped Ba(Fe1-xCox)(2)As-2 revealed by partial detwinning in a magnetic field PHYSICAL REVIEW B Chu, J., Analytis, J. G., Press, D., De Greve, K., Ladd, T. D., Yamamoto, Y., Fisher, I. R. 2010; 81 (21)
  • Ultrafast optical spin echo in a single quantum dot NATURE PHOTONICS Press, D., De Greve, K., McMahon, P. L., Ladd, T. D., Friess, B., Schneider, C., Kamp, M., Hoefling, S., Forchel, A., Yamamoto, Y. 2010; 4 (6): 367-370
  • Fluorine-doped ZnSe for applications in quantum information processing PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Ladd, T. D., Sanaka, K., Yamamoto, Y., Pawlis, A., Lischka, K. 2010; 247 (6): 1543-1546
  • Hong-Ou-Mandel Dip Using Degenerate Photon Pairs from a Single Periodically Poled Lithium Niobate Waveguide with Integrated Mode Demultiplexer JAPANESE JOURNAL OF APPLIED PHYSICS Zhang, Q., Takesue, H., Langrock, C., Xie, X., Fejer, M. M., Yamamoto, Y. 2010; 49 (6)
  • Mott transitions of exciton polaritons and indirect excitons in a periodic potential PHYSICAL REVIEW B Byrnes, T., Recher, P., Yamamoto, Y. 2010; 81 (20)
  • Exciton-polariton Bose-Einstein condensation REVIEWS OF MODERN PHYSICS Deng, H., Haug, H., Yamamoto, Y. 2010; 82 (2): 1489-1537
  • Gain-Induced Trapping of Microcavity Exciton Polariton Condensates PHYSICAL REVIEW LETTERS Roumpos, G., Nitsche, W. H., Hoefling, S., Forchel, A., Yamamoto, Y. 2010; 104 (12)

    Abstract

    We have performed real and momentum space spectroscopy of exciton polariton condensates in a GaAs-based microcavity under nonresonant excitation with an intensity-stabilized laser. An effective trapping mechanism is revealed, which is due to the stimulated scattering gain inside the finite excitation spot combined with the short lifetime. We observe several quantized modes while the lowest state shows Heisenberg-limited real and momentum space distributions. The experimental findings are qualitatively reproduced by an open dissipative Gross-Pitaevskii equation model.

    View details for DOI 10.1103/PhysRevLett.104.126403

    View details for Web of Science ID 000276072400038

    View details for PubMedID 20366554

  • DISTRIBUTED QUANTUM COMPUTATION ARCHITECTURE USING SEMICONDUCTOR NANOPHOTONICS INTERNATIONAL JOURNAL OF QUANTUM INFORMATION Van Meter, R., Ladd, T. D., Fowler, A. G., Yamamoto, Y. 2010; 8 (1-2): 295-323
  • Higher order coherence of exciton-polariton condensates PHYSICAL REVIEW B Horikiri, T., Schwendimann, P., Quattropani, A., Hoefling, S., Forchel, A., Yamamoto, Y. 2010; 81 (3)
  • Bose-Einstein condensation of exciton-polaritons RIVISTA DEL NUOVO CIMENTO Yamamoto, Y., Deng, H., Haug, H. 2010; 33 (10): 591-631
  • Vortex-antivortex pair dynamics in an exciton-polariton condensate NEW JOURNAL OF PHYSICS Fraser, M. D., Roumpos, G., Yamamoto, Y. 2009; 11
  • Unconditional Security of Single-Photon Differential Phase Shift Quantum Key Distribution PHYSICAL REVIEW LETTERS Wen, K., Tamaki, K., Yamamoto, Y. 2009; 103 (17)

    Abstract

    In this Letter, we prove the unconditional security of the single-photon differential phase shift quantum key distribution (DPS-QKD) protocol, based on the conversion to an equivalent entanglement-based protocol. We estimate the upper bound of the phase error rate from the bit error rate, and show that the DPS-QKD protocol can generate an unconditionally secure key when the bit error rate is not greater than 4.12%. This proof is the first step to the unconditional security proof of a coherent state DPS-QKD.

    View details for DOI 10.1103/PhysRevLett.103.170503

    View details for Web of Science ID 000271164500007

    View details for PubMedID 19905739

  • Indistinguishable Photons from Independent Semiconductor Nanostructures PHYSICAL REVIEW LETTERS Sanaka, K., Pawlis, A., Ladd, T. D., Lischka, K., Yamamoto, Y. 2009; 103 (5)

    Abstract

    We demonstrate quantum interference between photons generated by the radiative decay processes of excitons that are bound to isolated fluorine donor impurities in ZnSe/ZnMgSe quantum-well nanostructures. The ability to generate single photons from these devices is confirmed by autocorrelation experiments, and the indistinguishability of photons emitted from two independent nanostructures is confirmed via a Hong-Ou-Mandel dip. These results indicate that donor impurities in appropriately engineered semiconductor structures can portray atomlike homogeneity and coherence properties, potentially enabling scalable technologies for future large-scale optical quantum computers and quantum communication networks.

    View details for DOI 10.1103/PhysRevLett.103.053601

    View details for Web of Science ID 000268618300031

    View details for PubMedID 19792497

  • Ultrafast Optical Spin Echo for Electron Spins in Semiconductors PHYSICAL REVIEW LETTERS Clark, S. M., Fu, K. C., Zhang, Q., Ladd, T. D., Stanley, C., Yamamoto, Y. 2009; 102 (24)

    Abstract

    Spin-based quantum computing and magnetic resonance techniques rely on the ability to measure the coherence time T(2) of a spin system. We report on the experimental implementation of all-optical spin echo to determine the T(2) time of a semiconductor electron-spin system. We use three ultrafast optical pulses to rotate spins an arbitrary angle and measure an echo signal as the time between pulses is lengthened. Unlike previous spin-echo techniques using microwaves, ultrafast optical pulses allow clean T(2) measurements of systems with dephasing times (T_{2};{*}) fast in comparison to the time scale for microwave control. This demonstration provides a step toward ultrafast optical dynamic decoupling of spin-based qubits.

    View details for DOI 10.1103/PhysRevLett.102.247601

    View details for Web of Science ID 000267197900065

    View details for PubMedID 19659047

  • Signature of the microcavity exciton-polariton relaxation mechanism in the polarization of emitted light PHYSICAL REVIEW B Roumpos, G., Lai, C., Liew, T. C., Rubo, Y. G., Kavokin, A. V., Yamamoto, Y. 2009; 79 (19)
  • Megabits secure key rate quantum key distribution NEW JOURNAL OF PHYSICS Zhang, Q., Takesue, H., Honjo, T., Wen, K., Hirohata, T., Suyama, M., Takiguchi, Y., Kamada, H., Tokura, Y., Tadanaga, O., Nishida, Y., Asobe, M., Yamamoto, Y. 2009; 11
  • Generation and application of multi-path cat states of light NEW JOURNAL OF PHYSICS Ishida, N., Ota, Y., Yamamoto, Y. 2009; 11
  • Driven to perfection NATURE PHYSICS Santori, C., Yamamoto, Y. 2009; 5 (3): 173-174

    View details for DOI 10.1038/nphys1215

    View details for Web of Science ID 000264446600005

  • Monolithic integration of quantum dot containing microdisk microcavities coupled to air-suspended waveguides APPLIED PHYSICS LETTERS Koseki, S., Zhang, B., De Greve, K., Yamamoto, Y. 2009; 94 (5)

    View details for DOI 10.1063/1.3078522

    View details for Web of Science ID 000263167000010

  • Waveguide-based single-pixel up-conversion infrared spectrometer OPTICS EXPRESS Zhang, Q., Langrock, C., Fejer, M. M., Yamamoto, Y. 2008; 16 (24): 19557-19561

    Abstract

    A periodically poled lithium niobate (PPLN) waveguide-based single-pixel up-conversion infrared spectrometer was demonstrated. Sum-frequency generation between a 1.5-microm-band scanning pump laser and a 1.3-microm-band signal generated visible radiation which was detected by a silicon single-photon detector. The up-conversion spectrometer's sensitivity was two-orders-of-magnitude higher than that of a commercial optical spectrum analyzer.

    View details for Web of Science ID 000261561900016

    View details for PubMedID 19030042

  • Complete quantum control of a single quantum dot spin using ultrafast optical pulses NATURE Press, D., Ladd, T. D., Zhang, B., Yamamoto, Y. 2008; 456 (7219): 218-221

    Abstract

    A basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit. For qubits based on electron spin, a universal single-qubit gate is realized by a rotation of the spin by any angle about an arbitrary axis. Driven, coherent Rabi oscillations between two spin states can be used to demonstrate control of the rotation angle. Ramsey interference, produced by two coherent spin rotations separated by a variable time delay, demonstrates control over the axis of rotation. Full quantum control of an electron spin in a quantum dot has previously been demonstrated using resonant radio-frequency pulses that require many spin precession periods. However, optical manipulation of the spin allows quantum control on a picosecond or femtosecond timescale, permitting an arbitrary rotation to be completed within one spin precession period. Recent work in optical single-spin control has demonstrated the initialization of a spin state in a quantum dot, as well as the ultrafast manipulation of coherence in a largely unpolarized single-spin state. Here we demonstrate complete coherent control over an initialized electron spin state in a quantum dot using picosecond optical pulses. First we vary the intensity of a single optical pulse to observe over six Rabi oscillations between the two spin states; then we apply two sequential pulses to observe high-contrast Ramsey interference. Such a two-pulse sequence realizes an arbitrary single-qubit gate completed on a picosecond timescale. Along with the spin initialization and final projective measurement of the spin state, these results demonstrate a complete set of all-optical single-qubit operations.

    View details for DOI 10.1038/nature07530

    View details for Web of Science ID 000261039300035

    View details for PubMedID 19005550

  • Long-distance entanglement-based quantum key distribution over optical fiber OPTICS EXPRESS Honjo, T., Nam, S. W., Takesue, H., Zhang, Q., Kamada, H., Nishida, Y., Tadanaga, O., Asobe, M., Baek, B., Hadfield, R. H., Miki, S., Fujiwara, M., Sasaki, M., Wang, Z., Inoue, K., Yamamoto, Y. 2008; 16 (23): 19118-19126

    Abstract

    We report the first entanglement-based quantum key distribution (QKD) experiment over a 100-km optical fiber. We used superconducting single photon detectors based on NbN nanowires that provide high-speed single photon detection for the 1.5-mum telecom band, an efficient entangled photon pair source that consists of a fiber coupled periodically poled lithium niobate waveguide and ultra low loss filters, and planar lightwave circuit Mach-Zehnder interferometers (MZIs) with ultra stable operation. These characteristics enabled us to perform an entanglement-based QKD experiment over a 100-km optical fiber. In the experiment, which lasted approximately 8 hours, we successfully generated a 16 kbit sifted key with a quantum bit error rate of 6.9 % at a rate of 0.59 bits per second, from which we were able to distill a 3.9 kbit secure key.

    View details for Web of Science ID 000260866000064

    View details for PubMedID 19582004

  • Ultrafast control of donor-bound electron spins with single detuned optical pulses NATURE PHYSICS Fu, K. C., Clark, S. M., Santori, C., Stanley, C. R., Holland, M. C., Yamamoto, Y. 2008; 4 (10): 780-784

    View details for DOI 10.1038/nphys1052

    View details for Web of Science ID 000259686800011

  • Observation of Bogoliubov excitations in exciton-polariton condensates NATURE PHYSICS Utsunomiya, S., Tian, L., Roumpos, G., Lai, C. W., Kumada, N., Fujisawa, T., Kuwata-Gonokami, M., Loeffler, A., Hoefling, S., Forchel, A., Yamamoto, Y. 2008; 4 (9): 700-705

    View details for DOI 10.1038/nphys1034

    View details for Web of Science ID 000259686400013

  • Quantum simulation of Fermi-Hubbard models in semiconductor quantum-dot arrays PHYSICAL REVIEW B Byrnes, T., Kim, N. Y., Kusudo, K., Yamamoto, Y. 2008; 78 (7)
  • GaAs microcavity exciton-polaritons in a trap PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Kim, N. Y., Lai, C., Utsunomiya, S., Roumpos, G., Fraser, M., Deng, H., Byrnes, T., Recher, P., Kumada, N., Fujisawa, T., Yamamoto, Y. 2008; 245 (6): 1076-1080
  • Distribution of Time-Energy Entanglement over 100 km fiber using superconducting single-photon detectors OPTICS EXPRESS Zhang, Q., Takesue, H., Nam, S. W., Langrock, C., Xie, X., Baek, B., Fejer, M. M., Yamamoto, Y. 2008; 16 (8): 5776-5781

    Abstract

    In this letter, we report an experimental realization of distributing entangled photon pairs over 100 km of dispersion-shifted fiber. In the experiment, we used a periodically poled lithium niobate waveguide to generate the time-energy entanglement and superconducting single-photon detectors to detect the photon pairs after 100 km. We also demonstrate that the distributed photon pairs can still be useful for quantum key distribution and other quantum communication tasks.

    View details for Web of Science ID 000255120300071

    View details for PubMedID 18542687

  • Lasing of donor-bound excitons in ZnSe microdisks PHYSICAL REVIEW B Pawlis, A., Panfilova, M., As, D. J., Lischka, K., Sanaka, K., Ladd, T. D., Yamamoto, Y. 2008; 77 (15)
  • Generation of 10-GHz clock sequential time-bin entanglement OPTICS EXPRESS Zhang, Q., Langrock, C., Takesue, H., Xie, X., Fejer, M., Yamamoto, Y. 2008; 16 (5): 3293-3298

    Abstract

    This letter reports telecom-band sequential time-bin entangled photon-pair generation at a repetition rate of 10 GHz in periodically poled reverse-proton-exchange lithium niobate waveguides based on mode demultiplexing. With up-conversion single-photon detectors, we observed an entangled-photon-pair flux of 313 Hz and a two-photon-interference-fringe visibility of 85.32% without subtraction of accidental noise contributions.

    View details for Web of Science ID 000254121300049

    View details for PubMedID 18542417

  • Strongly correlated polaritons in a two-dimensional array of photonic crystal microcavities PHYSICAL REVIEW A Na, N., Utsunomiya, S., Tian, L., Yamamoto, Y. 2008; 77 (3)
  • Coherent zero-state and p-state in an exciton-polariton condensate array NATURE Lai, C. W., Kim, N. Y., Utsunomiya, S., Roumpos, G., Deng, H., Fraser, M. D., Byrnes, T., Recher, P., Kumada, N., Fujisawa, T., Yamamoto, Y. 2007; 450 (7169): 529-U8

    Abstract

    The effect of quantum statistics in quantum gases and liquids results in observable collective properties among many-particle systems. One prime example is Bose-Einstein condensation, whose onset in a quantum liquid leads to phenomena such as superfluidity and superconductivity. A Bose-Einstein condensate is generally defined as a macroscopic occupation of a single-particle quantum state, a phenomenon technically referred to as off-diagonal long-range order due to non-vanishing off-diagonal components of the single-particle density matrix. The wavefunction of the condensate is an order parameter whose phase is essential in characterizing the coherence and superfluid phenomena. The long-range spatial coherence leads to the existence of phase-locked multiple condensates in an array of superfluid helium, superconducting Josephson junctions or atomic Bose-Einstein condensates. Under certain circumstances, a quantum phase difference of pi is predicted to develop among weakly coupled Josephson junctions. Such a meta-stable pi-state was discovered in a weak link of superfluid 3He, which is characterized by a 'p-wave' order parameter. The possible existence of such a pi-state in weakly coupled atomic Bose-Einstein condensates has also been proposed, but remains undiscovered. Here we report the observation of spontaneous build-up of in-phase ('zero-state') and antiphase ('pi-state') 'superfluid' states in a solid-state system; an array of exciton-polariton condensates connected by weak periodic potential barriers within a semiconductor microcavity. These in-phase and antiphase states reflect the band structure of the one-dimensional polariton array and the dynamic characteristics of metastable exciton-polariton condensates.

    View details for DOI 10.1038/nature06334

    View details for Web of Science ID 000251158500042

    View details for PubMedID 18033292

  • Spatial coherence of a polariton condensate PHYSICAL REVIEW LETTERS Deng, H., Solomon, G. S., Hey, R., Ploog, K. H., Yamamoto, Y. 2007; 99 (12)

    Abstract

    We perform Young's double-slit experiment to study the spatial coherence properties of a two-dimensional dynamic condensate of semiconductor microcavity polaritons. The coherence length of the system is measured as a function of the pump rate, which confirms a spontaneous buildup of macroscopic coherence in the condensed phase. An independent measurement reveals that the position and momentum uncertainty product of the condensate is close to the Heisenberg limit. An experimental realization of such a minimum uncertainty wave packet of the polariton condensate opens a door to coherent matter-wave phenomena such as Josephson oscillation, superfluidity, and solitons in solid state condensate systems.

    View details for DOI 10.1103/PhysRevLett.99.126403

    View details for Web of Science ID 000249668000053

    View details for PubMedID 17930529

  • Correlated photon-pair generation in reverse-proton-exchange PPLN waveguides with integrated mode demultiplexer at 10 GHz clock OPTICS EXPRESS Zhang, Q., Xie, X., Takesue, H., Nam, S. W., Langrock, C., Fejer, M. M., Yamamoto, Y. 2007; 15 (16): 10288-10293

    Abstract

    We report 10-ps correlated photon pair generation in periodically-poled reverse-proton-exchange lithium niobate waveguides with integrated mode demultiplexer at a wavelength of 1.5-mum and a clock of 10 GHz. Using superconducting single photon detectors, we observed a coincidence to accidental count ratio (CAR) as high as 4000. The developed photon-pair source may find broad application in quantum information systems as well as quantum entanglement experiments.

    View details for Web of Science ID 000248753100040

    View details for PubMedID 19547378

  • Microcavity modified spontaneous emission of single quantum dots PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Solomon, G. S., Pelton, M., Yamamoto, Y. 2007; 244 (8): 2792-2802
  • Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses PHYSICAL REVIEW LETTERS Clark, S. M., Fu, K. C., Ladd, T. D., Yamamoto, Y. 2007; 99 (4)

    Abstract

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

    View details for DOI 10.1103/PhysRevLett.99.040501

    View details for Web of Science ID 000248345800005

    View details for PubMedID 17678343

  • Tomonaga-luttinger liquid features in ballistic single-walled carbon nanotubes: Conductance and shot noise PHYSICAL REVIEW LETTERS Kim, N. Y., Recher, P., Oliver, W. D., Yamamoto, Y., Kong, J., Dai, H. 2007; 99 (3)

    Abstract

    We study the electrical transport properties of well-contacted ballistic single-walled carbon nanotubes in a three-terminal configuration at low temperatures. We observe signatures of strong electron-electron interactions: the conductance exhibits bias-voltage-dependent amplitudes of quantum interference oscillation, and both the current noise and Fano factor manifest bias-voltage-dependent power-law scalings. We analyze our data within the Tomonaga-Luttinger liquid model using the nonequilibrium Keldysh formalism and find qualitative and quantitative agreement between experiment and theory.

    View details for DOI 10.1103/PhyRevLett.99.036802

    View details for Web of Science ID 000248194700038

    View details for PubMedID 17678308

  • Quantum simulator for the Hubbard model with long-range Coulomb interactions using surface acoustic waves PHYSICAL REVIEW LETTERS Byrnes, T., Recher, P., Kim, N. Y., Utsunomiya, S., Yamamoto, Y. 2007; 99 (1)

    Abstract

    An experimental scheme for a quantum simulator of strongly correlated electrons is proposed. Our scheme employs electrons confined in a two-dimensional electron gas in a GaAs/AlGaAs heterojunction. Two surface acoustic waves are then induced in the substrate, creating a two-dimensional "egg-carton" potential. The dynamics of the electrons in this potential are described by a Hubbard model with long-range Coulomb interactions. Estimates of the Hubbard parameters suggest that observations of quantum phase transition phenomena are within experimental reach.

    View details for DOI 10.1103/PhysRevLett.99.016405

    View details for Web of Science ID 000247819900035

    View details for PubMedID 17678174

  • Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors NATURE PHOTONICS Takesue, H., Nam, S. W., Zhang, Q., Hadfield, R. H., Honjo, T., Tamaki, K., Yamamoto, Y. 2007; 1 (6): 343-348
  • Generation and transfer of single photons on a photonic crystal chip OPTICS EXPRESS Englund, D., Faraon, A., Zhang, B., Yamamoto, Y., Vuckovic, J. 2007; 15 (9): 5550-5558

    Abstract

    We present a basic building block of a quantum network consisting of a quantum dot coupled to a source cavity, which in turn is coupled to a target cavity via a waveguide. The single photon emission from the high-Q/V source cavity is characterized by twelve-fold spontaneous emission (SE) rate enhancement, SE coupling efficiency beta ~ 0.98 into the source cavity mode, and mean wavepacket indistinguishability of ~67%. Single photons are efficiently transferred into the target cavity via the waveguide, with a target/source field intensity ratio of 0.12 +/- 0.01. This system shows great promise as a building block of future on-chip quantum information processing systems.

    View details for Web of Science ID 000246395000033

    View details for PubMedID 19532812

  • Dynamics of quantum dot photonic crystal lasers APPLIED PHYSICS LETTERS Ellis, B., Fushman, I., Englund, D., Zhang, B., Yamamoto, Y., Vuckovic, J. 2007; 90 (15)

    View details for DOI 10.1063/1.2720753

    View details for Web of Science ID 000245690700002

  • Photon antibunching from a single quantum-dot-microcavity system in the strong coupling regime PHYSICAL REVIEW LETTERS Press, D., Goetzinger, S., Reitzenstein, S., Hofmann, C., Loeffler, A., Kamp, M., Forchel, A., Yamamoto, Y. 2007; 98 (11)

    Abstract

    We observe antibunching in the photons emitted from a strongly coupled single quantum dot and pillar microcavity in resonance. When the quantum dot was spectrally detuned from the cavity mode, the cavity emission remained antibunched, and also anticorrelated from the quantum dot emission. Resonant pumping of the selected quantum dot via an excited state enabled these observations by eliminating the background emitters that are usually coupled to the cavity. This device demonstrates an on-demand single-photon source operating in the strong coupling regime, with a Purcell factor of 61+/-7 and quantum efficiency of 97%.

    View details for DOI 10.1103/PhysRevLett.98.117402

    View details for Web of Science ID 000244959300067

    View details for PubMedID 17501092

  • Quantum simulation of spin ordering with nuclear spins in a solid-state lattice PHYSICAL REVIEW B Roumpos, G., Master, C. P., Yamamoto, Y. 2007; 75 (9)
  • Algorithm-based analysis of collective decoherence in quantum computation JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Utsunomiya, S., Master, C. P., Yamamoto, Y. 2007; 24 (2): 198-208
  • Optical quantum information science - Introduction JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Sanders, B., Yamamoto, Y., Zeilinger, A. 2007; 24 (2)
  • 1.5-mu m single photon counting using polarization-independent up-conversion detector OPTICS EXPRESS Takesue, H., Diamanti, E., Langrock, C., Fejer, M. M., Yamamoto, Y. 2006; 14 (26): 13067-13072

    Abstract

    We report a 1.5- mum band polarization independent single photon detector based on frequency up-conversion in periodically poled lithium niobate (PPLN) waveguides. To overcome the polarization dependence of the PPLN waveguides, we employed a polarization diversity configuration composed of two up-conversion detectors connected with a polarization beam splitter. We experimentally confirmed polarization independent single photon counting using our detector. We undertook a proof-of-principle differential phase shift quantum key distribution experiment using the detector, and confirmed that the sifted key rate and error rate remained stable when the polarization state was changed during single photon transmission.

    View details for Web of Science ID 000243144600056

    View details for PubMedID 19532202

  • 100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors OPTICS EXPRESS Diamanti, E., Takesue, H., Langrock, C., Fejer, M. M., Yamamoto, Y. 2006; 14 (26): 13073-13082

    Abstract

    We present a quantum key distribution experiment in which keys that were secure against all individual eavesdropping attacks allowed by quantum mechanics were distributed over 100 km of optical fiber. We implemented the differential phase shift quantum key distribution protocol and used low timing jitter 1.55 microm single-photon detectors based on frequency up-conversion in periodically poled lithium niobate waveguides and silicon avalanche photodiodes. Based on the security analysis of the protocol against general individual attacks, we generated secure keys at a practical rate of 166 bit/s over 100 km of fiber. The use of the low jitter detectors also increased the sifted key generation rate to 2 Mbit/s over 10 km of fiber.

    View details for Web of Science ID 000243144600057

    View details for PubMedID 19532203

  • Tomonaga-Luttinger liquid correlations and Fabry-Perot interference in conductance and finite-frequency shot noise in a single-walled carbon nanotube PHYSICAL REVIEW B Recher, P., Kim, N. Y., Yamamoto, Y. 2006; 74 (23)
  • A gallium-nitride single-photon source operating at 200K NATURE MATERIALS Kako, S., Santori, C., Hoshino, K., Goetzinger, S., Yamamoto, Y., Arakawa, Y. 2006; 5 (11): 887-892

    Abstract

    Fundamentally secure quantum cryptography has still not seen widespread application owing to the difficulty of generating single photons on demand. Semiconductor quantum-dot structures have recently shown great promise as practical single-photon sources, and devices with integrated optical cavities and electrical-carrier injection have already been demonstrated. However, a significant obstacle for the application of commonly used III-V quantum dots to quantum-information-processing schemes is the requirement of liquid-helium cryogenic temperatures. Epitaxially grown gallium nitride quantum dots embedded in aluminium nitride have the potential for operation at much higher temperatures. Here, we report triggered single-photon emission from gallium nitride quantum dots at temperatures up to 200 K, a temperature easily reachable with thermo-electric cooling. Gallium nitride quantum dots also open a new wavelength region in the blue and near-ultraviolet portions of the spectrum for single-photon sources.

    View details for DOI 10.1038/nmat1763

    View details for Web of Science ID 000241732000023

    View details for PubMedID 17057699

  • Quantum degenerate exciton-polaritons in thermal equilibrium PHYSICAL REVIEW LETTERS Deng, H., Press, D., Gotzinger, S., Solomon, G. S., Hey, R., Ploog, K. H., Yamamoto, Y. 2006; 97 (14)

    Abstract

    We study the momentum distribution and relaxation dynamics of semiconductor microcavity polaritons by angle-resolved and time-resolved spectroscopy. Above a critical pump level, the thermalization time of polaritons at positive detunings becomes shorter than their lifetime, and the polaritons form a quantum degenerate Bose-Einstein distribution in thermal equilibrium with the lattice.

    View details for DOI 10.1103/PhysRevLett.97.146402

    View details for Web of Science ID 000241057100052

    View details for PubMedID 17155273

  • 10-GHz clock differential phase shift quantum key distribution experiment OPTICS EXPRESS Takesue, H., Diamanti, E., Langrock, C., Fejer, M. M., Yamamoto, Y. 2006; 14 (20): 9522-9530

    Abstract

    This paper reports the first quantum key distribution experiment implemented with a 10-GHz clock frequency. We used a 10-GHz actively mode-locked fiber laser as a source of short coherent pulses and single photon detectors based on frequency up-conversion in periodically poled lithium niobate waveguides. The use of short pulses and low-jitter upconversion detectors significantly reduced the bit errors caused by detector dark counts even after long-distance transmission of a weak coherent state pulse. We employed the differential phase shift quantum key distribution protocol, and generated sifted keys at a rate of 3.7 kbit/s over a 105 km fiber with a bit error rate of 9.7%.

    View details for Web of Science ID 000240981000069

    View details for PubMedID 19529339

  • Solid state ion trap: Lateral confinement of quantum well excitons by oscillating piezoelectric field SOLID STATE COMMUNICATIONS Na, Y. C., Yamamoto, Y. 2006; 140 (1): 28-32
  • Investigation of excitons bound to fluorine donors in ZnSe SEMICONDUCTOR SCIENCE AND TECHNOLOGY Pawlis, A., Sanaka, K., Gotzinger, S., Yamamoto, Y., Lischka, K. 2006; 21 (10): 1412-1415
  • Hybrid quantum repeater based on dispersive CQED interactions between matter qubits and bright coherent light NEW JOURNAL OF PHYSICS Ladd, T. D., van Loock, P., Nemoto, K., Munro, W. J., Yamamoto, Y. 2006; 8
  • Millisecond spin-flip times of donor-bound electrons in GaAs PHYSICAL REVIEW B Fu, K. C., Yeo, W., Clark, S., Santori, C., Stanley, C., Holland, M. C., Yamamoto, Y. 2006; 74 (12)
  • Time-domain simulation of Schrodinger equation to determine the effective potential induced by an oscillating standing wave JOURNAL OF APPLIED PHYSICS Na, Y. C., Yamamoto, Y. 2006; 100 (4)

    View details for DOI 10.1063/1.2234803

    View details for Web of Science ID 000240236800143

  • Hybrid quantum repeater using bright coherent light PHYSICAL REVIEW LETTERS van Loock, P., Ladd, T. D., Sanaka, K., Yamaguchi, F., Nemoto, K., Munro, W. J., Yamamoto, Y. 2006; 96 (24)

    Abstract

    We describe a quantum repeater protocol for long-distance quantum communication. In this scheme, entanglement is created between qubits at intermediate stations of the channel by using a weak dispersive light-matter interaction and distributing the outgoing bright coherent-light pulses among the stations. Noisy entangled pairs of electronic spin are then prepared with high success probability via homodyne detection and postselection. The local gates for entanglement purification and swapping are deterministic and measurement-free, based upon the same coherent-light resources and weak interactions as for the initial entanglement distribution. Finally, the entanglement is stored in a nuclear-spin-based quantum memory. With our system, qubit-communication rates approaching 100 Hz over 1280 km with fidelities near 99% are possible for reasonable local gate errors.

    View details for DOI 10.1103/PhysRevLett.96.240501

    View details for Web of Science ID 000238487900004

    View details for PubMedID 16907223

  • 1.5 mu m photon-counting optical time-domain reflectometry with a single-photon detector based on upconversion in a periodically poled lithium niobate waveguide OPTICS LETTERS Diamanti, E., Langrock, C., Fejer, M. M., Yamamoto, Y., Takesue, H. 2006; 31 (6): 727-729

    Abstract

    Optical time-domain reflectometry (OTDR) is one of the most powerful tools in the characterization of optical fiber links. We demonstrate a photon-counting OTDR system at 1.5 microm with a single-photon detector, which combines frequency upconversion in a periodically poled lithium niobate waveguide and a silicon avalanche photodiode. The system exhibits high sensitivity, good spatial resolution, and short measurement time.

    View details for Web of Science ID 000235833400017

    View details for PubMedID 16544604

  • Highly nonclassical photon statistics in parametric down-conversion PHYSICAL REVIEW A Waks, E., Sanders, B. C., Diamanti, E., Yamamoto, Y. 2006; 73 (3)
  • Simulating lattice gauge theories on a quantum computer PHYSICAL REVIEW A Byrnes, T., Yamamoto, Y. 2006; 73 (2)
  • Generation of photon number states NEW JOURNAL OF PHYSICS Waks, E., Diamanti, E., Yamamoto, Y. 2006; 8
  • Security of differential-phase-shift quantum key distribution against individual attacks PHYSICAL REVIEW A Waks, E., Takesue, H., Yamamoto, Y. 2006; 73 (1)
  • Differential phase shift quantum key distribution experiment over 105km fibre NEW JOURNAL OF PHYSICS Takesue, H., Diamanti, E., Honjo, T., Langrock, C., Fejer, M. M., Inoue, K., Yamamoto, Y. 2005; 7
  • Performance of various quantum-key-distribution systems using 1.55-mu m up-conversion single-photon detectors PHYSICAL REVIEW A Diamanti, E., Takesue, H., Honjo, T., Inoue, K., Yamamoto, Y. 2005; 72 (5)
  • Coherent population trapping of electron spins in a high-purity n-type GaAs semiconductor PHYSICAL REVIEW LETTERS Fu, K. M., Santori, C., Stanley, C., Holland, M. C., Yamamoto, Y. 2005; 95 (18)

    Abstract

    In high-purity n-type GaAs under a strong magnetic field, we are able to isolate a lambda system composed of two Zeeman states of neutral-donor-bound electrons and the lowest Zeeman state of bound excitons. When the two-photon detuning of this system is zero, we observe a pronounced dip in the excited-state photoluminescence, indicating the creation of the coherent population-trapped state. Our data are consistent with a steady-state three-level density-matrix model. The observation of coherent population trapping in GaAs indicates that this and similar semiconductor systems could be used for various electromagnetically induced transparency type experiments.

    View details for DOI 10.1103/PhysRevLett.95.187405

    View details for Web of Science ID 000232887400072

    View details for PubMedID 16383948

  • HIV-1 infection initiates changes in the expression of a wide array of genes in U937 promonocytes and HUT78 T cells VIRUS RESEARCH Wen, W. R., Chen, S. T., Cao, Y., Zhu, Y. H., Yamamoto, Y. 2005; 113 (1): 26-35

    Abstract

    Human monocytes/macrophages (M/M) are the major targets for human immunodeficiency virus type 1 (HIV-1) infection. To characterize the global effects of acute HIV-1 infection on gene expression in M/M, the expression levels of 550 host cell RNA transcripts in U937 human promonocytes at 2-3 days after HIV-1 infection were assessed using cDNA microarray analysis and were compared to those in the infected HUT78, a CD4+ T cell line. Confirmed by semiquantitative RT-PCR, our results showed that 12 genes were up-regulated and 26 genes were down-regulated in the infected U937 cells at 2-3 days post-infection, whereas 8 genes were up-regulated and 20 genes were down-regulated in the infected HUT78 cells at 2-3 days post-infection. These genes encode a host of proteins with divergent functions in a variety of cellular processes including apoptosis (FAS, Fas ligand, PIN, HSP90beta, bcl-2, bcl-x), cell signal transduction (Ras, RGS1, IRF-1, STAT3), receptor-mediated signaling transduction (CD71, CD69, CD3delta), cell cycle and growth (c-myc, cytokines, kinase), transcriptional regulation (EWS, CREB-2), and chemotaxis (beta-chemokines, RANTES), supporting the general effects of HIV-1 infection on cells of different origin. Although most identified genes were regulated similarly in both infected cell lines, differences in gene regulation, such as c-myc, CD71, CD69, and beta-chemokines, between the two infected cell lines were also identified in this study. These differences may further our understanding of the pathogenicity of HIV and enable the discovery of novel therapeutic approach for AIDS.

    View details for DOI 10.1016/j.virusres.2005.04.002

    View details for Web of Science ID 000232022200003

    View details for PubMedID 15885842

  • Photon correlation studies of single GaN quantum dots APPLIED PHYSICS LETTERS Santori, C., Gotzinger, S., Yamamoto, Y., Kako, S., Hoshino, K., Arakawa, Y. 2005; 87 (5)

    View details for DOI 10.1063/1.2006987

    View details for Web of Science ID 000230886100023

  • Controlling the spontaneous emission rate of single quantum dots in a two-dimensional photonic crystal PHYSICAL REVIEW LETTERS Englund, D., Fattal, D., Waks, E., Solomon, G., Zhang, B., Nakaoka, T., Arakawa, Y., Yamamoto, Y., Vuckovic, J. 2005; 95 (1)

    Abstract

    We observe large spontaneous emission rate modification of individual InAs quantum dots (QDs) in a 2D photonic crystal with a modified, high-Q single-defect cavity. Compared to QDs in a bulk semiconductor, QDs that are resonant with the cavity show an emission rate increase of up to a factor of 8. In contrast, off-resonant QDs indicate up to fivefold rate quenching as the local density of optical states is diminished in the photonic crystal. In both cases, we demonstrate photon antibunching, showing that the structure represents an on-demand single photon source with a pulse duration from 210 ps to 8 ns. We explain the suppression of QD emission rate using finite difference time domain simulations and find good agreement with experiment.

    View details for DOI 10.1103/PhysRevLett.95.013904

    View details for Web of Science ID 000230275500032

    View details for PubMedID 16090618

  • Highly efficient single-photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNbO3 waveguides OPTICS LETTERS Langrock, C., Diamanti, E., Roussev, R. V., Yamamoto, Y., Fejer, M. M., Takesue, H. 2005; 30 (13): 1725-1727

    Abstract

    Conventional single-photon detectors at communication wavelengths suffer from low quantum efficiencies and large dark counts. We present a single-photon detection system, operating at communication wavelengths, based on guided-wave frequency upconversion in a nonlinear crystal with an overall system detection efficiency (upconversion + detection) exceeding 46% at 1.56 microm. This system consists of a fiber-pigtailed reverse-proton-exchanged periodically poled LiNbO3 waveguide device in conjunction with a silicon-based single-photon counting module.

    View details for Web of Science ID 000230193000043

    View details for PubMedID 16075551

  • Magnetic mesa structures fabricated by reactive ion etching with CO/NH3/Xe plasma chemistry for an all-silicon quantum computer NANOTECHNOLOGY Wang, D. F., Takahashi, A., Matsumoto, Y., Itoh, K. M., Yamamoto, Y., Ono, T., Esashi, M. 2005; 16 (6): 990-994
  • Optical pumping of Si-29 nuclear spins in bulk silicon at high magnetic field and liquid helium temperature PHYSICAL REVIEW B Verhulst, A. S., Rau, I. G., Yamamoto, Y., Itoh, K. M. 2005; 71 (23)
  • Fabrication of InAs quantum dots in AlAs/GaAs DBR pillar microcavities for single photon sources JOURNAL OF APPLIED PHYSICS Zhang, B. Y., Solomon, G. S., Pelton, M., Plant, J., Santori, C., Vuckovic, J., Yamamoto, Y. 2005; 97 (7)

    View details for DOI 10.1063/1.1882764

    View details for Web of Science ID 000228287300018

  • Coherence time of decoupled nuclear spins in silicon PHYSICAL REVIEW B Ladd, T. D., Maryenko, D., Yamamoto, Y., Abe, E., Itoh, K. M. 2005; 71 (1)
  • Fluctuations and noise in photonics and quantum optics: a special issue in memory of Hermann Haus JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS Abbott, D., Shapiro, J. H., Yamamoto, Y. 2004; 6 (8): S621-S622
  • Single-photon generation with InAs quantum dots NEW JOURNAL OF PHYSICS Santori, C., Fattal, D., Vuckovic, J., Solomon, G. S., Yamamoto, Y. 2004; 6
  • Semiconductor microcavity as a spin-dependent optoelectronic device PHYSICAL REVIEW B Shelykh, I., Kavokin, K. V., Kavokin, A. V., Malpuech, G., Bigenwald, P., Deng, H., Weihs, G., Yamamoto, Y. 2004; 70 (3)
  • Submicrosecond correlations in photoluminescence from InAs quantum dots PHYSICAL REVIEW B Santori, C., Fattal, D., Vuckovic, J., Solomon, G. S., Waks, E., Yamamoto, Y. 2004; 69 (20)
  • Direct observation of nonclassical photon statistics in parametric down-conversion PHYSICAL REVIEW LETTERS Waks, E., Diamanti, E., Sanders, B. C., Bartlett, S. D., Yamamoto, Y. 2004; 92 (11)

    Abstract

    We employ a high quantum efficiency photon number counter to determine the photon number distribution of the output field from a parametric down-converter. The raw photocount data directly demonstrates that the source is nonclassical by 40 standard deviations, and correcting for the quantum efficiency yields a direct observation of oscillations in the photon number distribution.

    View details for DOI 10.1103/PhysRevLett.92.113602

    View details for Web of Science ID 000220344400018

    View details for PubMedID 15089134

  • Optical detection of the spin state of a single nucleus in silicon PHYSICAL REVIEW B Fu, K. M., Ladd, T. D., Santori, C., Yamamoto, Y. 2004; 69 (12)
  • Polariton lasing in a microcavity PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Weihs, G., Deng, H., Snoke, D., Yamamoto, Y. 2004; 201 (4): 625-632
  • Entanglement formation and violation of Bell's inequality with a semiconductor single photon source PHYSICAL REVIEW LETTERS Fattal, D., Inoue, K., Vuckovic, J., Santori, C., Solomon, G. S., Yamamoto, Y. 2004; 92 (3)

    Abstract

    We report the generation of polarization-entangled photons, using a quantum dot single photon source, linear optics, and photodetectors. Two photons created independently are observed to violate Bell's inequality. The density matrix describing the polarization state of the postselected photon pairs is reconstructed and agrees well with a simple model predicting the quality of entanglement from the known parameters of the single photon source. Our scheme provides a method to create no more than one entangled photon pair per cycle after postselection, a feature useful to enhance quantum cryptography protocols based on shared entanglement.

    View details for DOI 10.1103/PhysRevLett.92.037903

    View details for Web of Science ID 000188392800061

    View details for PubMedID 14753911

  • Quantum teleportation with a quantum dot single photon source PHYSICAL REVIEW LETTERS Fattal, D., Diamanti, E., Inoue, K., Yamamoto, Y. 2004; 92 (3)

    Abstract

    We report the experimental demonstration of a quantum teleportation protocol with a semiconductor single photon source. Two qubits, a target and an ancilla, each defined by a single photon occupying two optical modes (dual-rail qubit), were generated independently by the single photon source. Upon measurement of two modes from different qubits and postselection, the state of the two remaining modes was found to reproduce the state of the target qubit. In particular, the coherence between the target qubit modes was transferred to the output modes to a large extent. The observed fidelity is 80%, in agreement with the residual distinguishability between consecutive photons from the source. An improved version of this teleportation scheme using more ancillas is the building block of the recent Knill, Laflamme, and Milburn proposal for efficient linear optics quantum computation.

    View details for DOI 10.1103/PhysRevLett.92.037904

    View details for Web of Science ID 000188392800062

    View details for PubMedID 14753912

  • Polariton lasing vs. photon lasing in a semiconductor microcavity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Deng, H., Weihs, G., Snoke, D., Bloch, J., Yamamoto, Y. 2003; 100 (26): 15318-15323

    Abstract

    Nearly one decade after the first observation of Bose-Einstein condensation in atom vapors and realization of matter-wave (atom) lasers, similar concepts have been demonstrated recently for polaritons: half-matter, half-light quasiparticles in semiconductor microcavities. The half-light nature of polaritons makes polariton lasers promising as a new source of coherent and nonclassical light with extremely low threshold energy. The half-matter nature makes polariton lasers a unique test bed for many-body theories and cavity quantum electrodynamics. In this article, we present a series of experimental studies of a polariton laser, exploring its properties as a relatively dense degenerate Bose gas and comparing it to a photon laser achieved in the same structure. The polaritons have an effective mass that is twice the cavity photon effective mass, yet seven orders of magnitude less than the hydrogen atom mass; hence, they can potentially condense at temperatures seven orders of magnitude higher than those required for atom Bose-Einstein condensations. Accompanying the phase transition, a polariton laser emits coherent light but at a threshold carrier density two orders of magnitude lower than that needed for a normal photon laser in a same structure. It also is shown that, beyond threshold, the polariton population splits to a thermal equilibrium Bose-Einstein distribution at in-plane wave number k parallel > 0 and a nonequilibrium condensate at k parallel approximately 0, with a chemical potential approaching to zero. The spatial distributions and polarization characteristics of polaritons also are discussed as unique signatures of a polariton laser.

    View details for DOI 10.1073/pnas.2634328100

    View details for Web of Science ID 000187554600009

    View details for PubMedID 14673089

  • High-efficiency photon-number detection for quantum in-formation processing IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS Waks, E., Inoue, K., Oliver, W. D., Diamanti, E., Yamamoto, Y. 2003; 9 (6): 1502-1511
  • Noise in amplifiers JOURNAL OF LIGHTWAVE TECHNOLOGY Yamamoto, Y., Inoue, K. 2003; 21 (11): 2895-2915
  • Exciton-polariton lasing in a microcavity SEMICONDUCTOR SCIENCE AND TECHNOLOGY Weihs, G., Deng, H., Huang, R., Sugita, M., Tassone, F., Yamamoto, Y. 2003; 18 (10): S386-S394
  • Double and single peaks in nuclear magnetic resonance spectra of natural and Si-29-enriched single-crystal silicon PHYSICAL REVIEW B Verhulst, A. S., Maryenko, D., Yamamoto, Y., Itoh, K. M. 2003; 68 (5)
  • The Rashba effect within the coherent scattering formalism with applications to electron quantum optics JOURNAL OF SUPERCONDUCTIVITY Oliver, W. D., Feve, G., Yamamoto, Y. 2003; 16 (4): 719-733
  • Differential-phase-shift quantum key distribution using coherent light PHYSICAL REVIEW A Inoue, K., Waks, E., Yamamoto, Y. 2003; 68 (2)
  • Comment on "Single-mode spontaneous emission from a single quantum dot in a three-dimensional microcavity" - Solomon, Pelton, and Yamamoto reply PHYSICAL REVIEW LETTERS Solomon, G. S., Pelton, M., Yamamoto, Y. 2003; 90 (22)
  • Entanglement-based quantum key distribution without an entangled-photon source PHYSICAL REVIEW A Inoue, K., Santori, C., Waks, E., Yamamoto, Y. 2003; 67 (6)
  • Photonic crystal microcavities for cavity quantum electrodynamics with a single quantum dot APPLIED PHYSICS LETTERS Vuckovic, J., Yamamoto, Y. 2003; 82 (15): 2374-2376

    View details for DOI 10.1063/1.1567824

    View details for Web of Science ID 000182104900002

  • Efficiency of free-energy calculations of spin lattices by spectral quantum algorithms PHYSICAL REVIEW A Master, C. P., Yamaguchi, F., Yamamoto, Y. 2003; 67 (3)
  • Secure communication: Quantum cryptography with a photon turnstile NATURE Waks, E., Inoue, K., Santori, C., Fattal, D., Vuckovic, J., Solomon, G. S., Yamamoto, Y. 2002; 420 (6917): 762-762

    View details for DOI 10.1038/420762a

    View details for Web of Science ID 000179897300046

    View details for PubMedID 12490939

  • Efficient source of single photons: A single quantum dot in a micropost microcavity PHYSICAL REVIEW LETTERS Pelton, M., Santori, C., Vuckovic, J., Zhang, B. Y., Solomon, G. S., Plant, J., Yamamoto, Y. 2002; 89 (23)

    Abstract

    We have demonstrated efficient production of triggered single photons by coupling a single semiconductor quantum dot to a three-dimensionally confined optical mode in a micropost microcavity. The efficiency of emitting single photons into a single-mode traveling wave is approximately 38%, which is nearly 2 orders of magnitude higher than for a quantum dot in bulk semiconductor material. At the same time, the probability of having more than one photon in a given pulse is reduced by a factor of 7 as compared to light with Poissonian photon statistics.

    View details for DOI 10.1103/PhysRevLett.89.233602

    View details for Web of Science ID 000179362700020

    View details for PubMedID 12485008

  • Rashba effect within the coherent scattering formalism PHYSICAL REVIEW B Feve, G., Oliver, W. D., Aranzana, M., Yamamoto, Y. 2002; 66 (15)
  • Indistinguishable photons from a single-photon device NATURE Santori, C., Fattal, D., Vuckovic, J., Solomon, G. S., Yamamoto, Y. 2002; 419 (6907): 594-597

    Abstract

    Single-photon sources have recently been demonstrated using a variety of devices, including molecules, mesoscopic quantum wells, colour centres, trapped ions and semiconductor quantum dots. Compared with a Poisson-distributed source of the same intensity, these sources rarely emit two or more photons in the same pulse. Numerous applications for single-photon sources have been proposed in the field of quantum information, but most--including linear-optical quantum computation--also require consecutive photons to have identical wave packets. For a source based on a single quantum emitter, the emitter must therefore be excited in a rapid or deterministic way, and interact little with its surrounding environment. Here we test the indistinguishability of photons emitted by a semiconductor quantum dot in a microcavity through a Hong-Ou-Mandel-type two-photon interference experiment. We find that consecutive photons are largely indistinguishable, with a mean wave-packet overlap as large as 0.81, making this source useful in a variety of experiments in quantum optics and quantum information.

    View details for DOI 10.1038/nature01086

    View details for Web of Science ID 000178483100038

    View details for PubMedID 12374958

  • Condensation of semiconductor microcavity exciton polaritons SCIENCE Deng, H., Weihs, G., Santori, C., Bloch, J., Yamamoto, Y. 2002; 298 (5591): 199-202

    Abstract

    A phase transition from a classical thermal mixed state to a quantum-mechanical pure state of exciton polaritons is observed in a GaAs multiple quantum-well microcavity from the decrease of the second-order coherence function. Supporting evidence is obtained from the observation of a nonlinear threshold behavior in the pump-intensity dependence of the emission, a polariton-like dispersion relation above threshold, and a decrease of the relaxation time into the lower polariton state. The condensation of microcavity exciton polaritons is confirmed.

    View details for Web of Science ID 000178370500058

    View details for PubMedID 12364801

  • Security aspects of quantum key distribution with sub-Poisson light PHYSICAL REVIEW A Waks, E., Santori, C., Yamamoto, Y. 2002; 66 (4)
  • Optimization of three-dimensional micropost microcavities for cavity quantum electrodynamics PHYSICAL REVIEW A Vuckovic, J., Pelton, M., Scherer, A., Yamamoto, Y. 2002; 66 (2)
  • Polarization-correlated photon pairs from a single quantum dot PHYSICAL REVIEW B Santori, C., Fattal, D., Pelton, M., Solomon, G. S., Yamamoto, Y. 2002; 66 (4)
  • Differential phase shift quantum key distribution PHYSICAL REVIEW LETTERS Inoue, K., Waks, E., Yamamoto, Y. 2002; 89 (3)

    Abstract

    A novel quantum cryptography scheme is proposed, in which a single photon is prepared in a linear superposition state of three basis kets. A photon split to three pulses is sent from Alice to Bob, where the phase difference between sequential two pulses carries bit information. Bob measures the phase difference by passive differential phase detection. This scheme is suitable for fiber transmission systems and offers a key creation efficiency higher than conventional fiber-based BB84.

    View details for DOI 10.1103/PhysRevLett.89.037902

    View details for Web of Science ID 000176599500041

    View details for PubMedID 12144419

  • All-silicon quantum computer PHYSICAL REVIEW LETTERS Ladd, T. D., Goldman, J. R., Yamaguchi, F., Yamamoto, Y., Abe, E., Itoh, K. M. 2002; 89 (1)

    Abstract

    A solid-state implementation of a quantum computer composed entirely of silicon is proposed. Qubits are 29Si nuclear spins arranged as chains in a 28Si (spin-0) matrix with Larmor frequencies separated by a large magnetic field gradient. No impurity dopants or electrical contacts are needed. Initialization is accomplished by optical pumping, algorithmic cooling, and pseudo-pure state techniques. Magnetic resonance force microscopy is used for ensemble measurement.

    View details for DOI 10.1103/PhysRevLett.89.017901

    View details for Web of Science ID 000176285700049

    View details for PubMedID 12097071

  • Effect of coronary stent overexpansion on lumen size and intimal hyperplasia at follow-up AMERICAN JOURNAL OF CARDIOLOGY Kuriyama, N., Kobayashi, Y., Kuroda, N., Desai, K., Yamamoto, Y., Komiyama, N., Komuro, I., Fitzgerald, P. J. 2002; 89 (11): 1297-?

    View details for Web of Science ID 000175985300012

    View details for PubMedID 12031732

  • Security of quantum key distribution with entangled photons against individual attacks PHYSICAL REVIEW A Waks, E., Zeevi, A., Yamamoto, Y. 2002; 65 (5)
  • Exciton-polariton lasing and amplification based on exciton-exciton scattering in CdTe microcavity quantum wells PHYSICAL REVIEW B Huang, R., Yamamoto, Y., Andre, R., Bleuse, J., Muller, M., Ulmer-Tuffigo, H. 2002; 65 (16)
  • Time-resolved spectroscopy of multiexcitonic decay in an InAs quantum dot PHYSICAL REVIEW B Santori, C., Solomon, G. S., Pelton, M., Yamamoto, Y. 2002; 65 (7)
  • Three-dimensionally confined modes in micropost microcavities: Quality factors and Purcell factors IEEE JOURNAL OF QUANTUM ELECTRONICS Pelton, M., Vuckovic, J., Solomon, G. S., Scherer, A., Yamamoto, Y. 2002; 38 (2): 170-177
  • Electron entanglement via a quantum dot PHYSICAL REVIEW LETTERS Oliver, W. D., Yamaguchi, F., Yamamoto, Y. 2002; 88 (3)

    Abstract

    This Letter presents a method of electron entanglement generation. The system under consideration is a single-level quantum dot with one input and two output leads. The leads are arranged such that the dot is empty, single-electron tunneling is suppressed by energy conservation, and two-electron virtual cotunneling is allowed. Such a configuration effectively filters the singlet-state portion of a two-electron input, yielding a nonlocal spin-singlet state at the output leads. Coulomb interaction mediates the entanglement generation, and, in its absence, the singlet state vanishes. This approach is a four-wave mixing process analogous to the photon entanglement generated by a chi((3)) parametric amplifier.

    View details for DOI 10.1103/PhysRevB.88.037901

    View details for Web of Science ID 000173460200042

    View details for PubMedID 11801089

  • Single-mode spontaneous emission from a single quantum dot in a three-dimensional microcavity PHYSICAL REVIEW LETTERS Solomon, G. S., Pelton, M., Yamamoto, Y. 2001; 86 (17): 3903-3906

    Abstract

    The spontaneous emission from an isolated semiconductor quantum dot state has been coupled with high efficiency to a single, polarization-degenerate cavity mode. The InAs quantum dot is epitaxially formed and embedded in a planar epitaxial microcavity, which is processed into a post of submicron diameter. The single quantum dot spontaneous emission lifetime is reduced from the noncavity value of 1.3 ns to 280 ps, resulting in a single-mode spontaneous emission coupling efficiency of 78%.

    View details for Web of Science ID 000168338300052

    View details for PubMedID 11329353

  • Triggered single photons from a quantum dot PHYSICAL REVIEW LETTERS Santori, C., Pelton, M., Solomon, G., Dale, Y., Yamamoto, E. 2001; 86 (8): 1502-1505

    Abstract

    We demonstrate a new method for generating triggered single photons. After a laser pulse generates excitons inside a single quantum dot, electrostatic interactions between them and the resulting spectral shifts allow a single emitted photon to be isolated. Correlation measurements show a reduction of the two-photon probability to 0.12 times the value for Poisson light. Strong antibunching persists when the emission is saturated. The emitted photons are also polarized.

    View details for Web of Science ID 000167010000027

    View details for PubMedID 11290178

  • Lasing and squeezing of composite bosons in a semiconductor microcavity PHYSICAL REVIEW A Tassone, F., Yamamoto, Y. 2000; 62 (6)
  • Comment on "generation of phase states by two-photon absorption" - Ezaki et al. reply PHYSICAL REVIEW LETTERS Ezaki, H., Hanamura, E., Yamamoto, Y. 2000; 85 (5): 1137-1137
  • Magnet designs for a crystal-lattice quantum computer APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Goldman, J. R., Ladd, T. D., Yamaguchi, F., Yamamoto, Y. 2000; 71 (1): 11-17
  • Quantum point contacts in a density-tunable two-dimensional electron gas JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS Nuttinck, S., HASHIMOTO, K., Miyashita, S., Saku, T., Yamamoto, Y., Hirayama, Y. 2000; 39 (7A): L655-L657
  • Simultaneous Coulomb blockade for electrons and holes in p-n junctions: observation of Coulomb staircase and turnstile operation PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES Benson, O., Kim, J., Kan, H., Yamamoto, Y. 2000; 8 (1): 5-12
  • Decoherence in crystal lattice quantum computation APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Ladd, T. D., Goldman, J. R., Yamaguchi, F., Yamamoto, Y. 2000; 71 (1): 27-36
  • Semiconductor physics - Half-matter, half-light amplifier NATURE Yamamoto, Y. 2000; 405 (6787): 629-630
  • Efficient implementation of coupled logic gates for quantum computation PHYSICAL REVIEW A Leung, D. W., Chuang, I. L., Yamaguchi, F., Yamamoto, Y. 2000; 61 (4)
  • Regulated and entangled photons from a single quantum Dot Physical review letters Benson, O., Santori, C., Pelton, M., Yamamoto, Y. 2000; 84 (11): 2513-6

    Abstract

    We propose a new method of generating nonclassical optical field states. The method uses a semiconductor device, which consists of a single quantum dot as active medium embedded in a p- i- n junction and surrounded by a microcavity. Resonant tunneling of electrons and holes into the quantum dot ground states, together with the Pauli exclusion principle, produce regulated single photons or regulated pairs of photons. We propose that this device also has the unique potential to generate pairs of entangled photons at a well-defined repetition rate.

    View details for PubMedID 11018923

  • Hanbury brown and twiss-type experiment with electrons Science (New York, N.Y.) Oliver, W. D., Kim, J., Liu, R. C., Yamamoto, Y. 1999; 284 (5412): 299-301

    Abstract

    Fermion anti-bunching was directly observed by measuring the cross-covariance of the current fluctuations of partitioned electrons. A quantum point contact was used to inject single-mode electrons into a mesoscopic electron beam splitter device. The beam splitter output currents showed negative cross-covariance, indicating that the electrons arrived individually at the beam splitter and were randomly partitioned into two output channels. As the relative time delay between the outputs was changed, the observed ringing in the cross-covariance was consistent with the bandwidths used to monitor the fluctuations. The result demonstrates a fermion complement to the Hanbury Brown and Twiss experiment for photons.

    View details for PubMedID 10195891

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