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- Kiyoshi Tamaki, Masato Koashi, Nobuyuki Imoto
- Physical review letters
- 2003

We prove the unconditional security of the Bennett 1992 protocol, by using a reduction to an entanglement distillation protocol initiated by a local filtering process. The bit errors and the phase errors are correlated after the filtering, and we can bound the amount of phase errors from the observed bit errors by an estimation method involvingâ€¦ (More)

- Yoritoshi Adachi, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto
- Physical review letters
- 2007

We propose an efficient quantum key distribution protocol based on the photon-pair generation from parametric down-conversion (PDC). It uses the same experimental setup as the conventional protocol, but a refined data analysis enables detection of photon-number splitting attacks by utilizing information from a built-in decoy state. Assuming the use ofâ€¦ (More)

We propose a simple probabilistic optical gate to expand polarization entangled W states. The gate uses one polarization-dependent beamsplitter and a horizontally polarized single photon as an ancilla. The gate post-selectively expands N -photon W states to (N + 1)-photon W states. A feasibility analysis considering the realistic experimental conditionsâ€¦ (More)

Junichi Shimamura, 2, 3 Åžahin Kaya Ã–zdemir, 3, 4 Fumiaki Morikoshi, and Nobuyuki Imoto 3, 4, 5 1 Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, JAPAN 2 SORST Research Team for Interacting Carrier Electronics CREST Research Team for Photonic Quantum Information The Graduate University for Advancedâ€¦ (More)

Effects of a corrupt source on the dynamics of simultaneous move strategic games are analyzed both for classical and quantum settings. The corruption rate dependent changes in the payoffs and strategies of the players are observed. It is shown that there is a critical corruption rate at which the players lose their quantum advantage, and that the classicalâ€¦ (More)

- R Ikuta, Yoshiaki Kusaka, +4 authors Nobuyuki Imoto
- Nature communications
- 2011

Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversionâ€¦ (More)

- Takashi Yamamoto, Masato Koashi, Sahin Kaya Ozdemir, Nobuyuki Imoto
- Nature
- 2003

Entanglement is considered to be one of the most important resources in quantum information processing schemes, including teleportation, dense coding and entanglement-based quantum key distribution. Because entanglement cannot be generated by classical communication between distant parties, distribution of entangled particles between them is necessary.â€¦ (More)

- Taihei Yamamoto, Masato Koashi, Nobuyuki Imoto
- Technical Digest. CLEO/Pacific Rim 2001. 4thâ€¦
- 2001

An experimental scheme for concentrating entanglement in partially entangled photon pairs is proposed. A practical realization of the proposed scheme is discussed, which uses imperfect photon detectors and spontaneous parametric down-conversion as a photon source. This scheme also works for purifying a class of mixed states.

- Toshiyuki Tashima, Tetsuroh Wakatsuki, Sahin Kaya Ozdemir, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto
- Physical review letters
- 2009

We propose and experimentally demonstrate a transformation of two Einstein-Podolsky-Rosen photon pairs distributed among three parties into a three-photon W state using local operations and classical communication. We then characterize the final state using quantum state tomography on the three-photon state and on its marginal bipartite states. The fidelityâ€¦ (More)