Laboratory of Optical Processing and Networking,
Graduate School of Information Science and Technology / School of Engineering, Hokkaido University

Quantum Key Distribution (QKD) enables two remote parties to share cryptographic keys, security of which is guaranteed by law of quantum mechanics. Recently, QKD technology is getting mature and expected to provide a practical solution for highly-security-demanding applications.
We study method for quantitative certification of the security, information theoretical secure protocols with QKD-generated key, and technology for quantum network.
(Photo shows a quantum commnunication board developed by NEC.)

Quantum protocols are proposed to perform impossible tasks for conventional information technology. We study the methodology for quantum system construction with photons to realize the proposed protocols.
We have demonstrated Quantum Fourier Transform (QFT) followed by measurement and Quantum Leader Election. We consider to perform functions of quantum circuits even with imperfect devices.
(Photo shows QFT circuit constructed with off-the-shelf photonic devices)

Development of quantum devices is indispensable for the experimantal studies of quantum information science. We study photon detectors, quantum gates, and entanglement photon-pair generators. We also explore combination of photons and electrons to realize new functional quantum devices.
(Figure shows experimental scheme of entangled photon-pair generation)

Recenly, research interest for low-power optical interconnection has been growing, as is seen in "Light Peak" by Intel. We have deloped a highly sensitive nonlinear optical device using Sn₂P₂S₂ in collaboration with over-seas researchers. In this device, light itself creates a waveguide to route the optimal path. The device will eliminate the need for precise alignment of optics. It will provide a simple and efficient connection between optical fibers and small waveguiding deices such as photonic crystal devices.
(Figure shows experimantal set-up for a self-genarating waveguide.)

We study mux-demux in multi-mode optical communication and dynamic photonic routing. We focus on the photo-refractive devices, which are expected to reconfigure the functions and the optical paths autonomously according to the changes of the optical signals.
(Figure shows a dynamically reconfigurable optical filter.)

We study advanced optical communincation between satellites with phase conjugation mirrors, which will reconstuct the optical path autonomously according the optical axis change and will reduce the stray light.

As post Blu-ray high-density optical recording techology, interest in holographic memories has been increasing. The holographic memories, with three dimensional recording, is expected to be suitable for high-density recording. We have developed technology to increasing density of the holographic memories. We study novel multiplex recording, multi-value modulation, digital coherent technique for optical discs, low-power optical recording. Our aim is to realize optical discs with peta-Bite capacity, and a number of patents have been applied as a result of our extensive research.
(Figure shows the proposed holographic memory system.)