Overview of Quantum Optics and Optical Materials Research

Takaaki Mukai
Physical Science Laboratory

@In the fields of quantum optics and optical materials we pursue our studies for the development of core-technologies that will innovate optical communications and optical signal processing as well as for the scientific progress of the field. Optical State Control Research Group, Ultrafast Optical Physics Research Group, Optical Device Physics Research Group and Photonic Nanostructure Research Group are engaged in the subjects listed below.

Quantum State Control Research Group
(‚P)Quantum communication and information processing (quantum cryptography/protocols, entanglement, and computing).
(‚Q)Atom optics (Bose-Einstein condensation of alkali atoms).

Ultrafast Optical Physics Research Group
(‚P)High-irradiance, short-pulse soft X-ray generation from femtosecond laser-produced plasma and its application to materials science.
(‚Q)(2) Ultrafast laser pulse induced terahertz radiation and its application.

Optical Device Physics Research Group
(‚P)Coherent control of excitonic and spin states in quantum dots & wires.
(‚Q)Optical properties in nitride-semiconductors and their device applications.
(‚R)Nano-scale fabrication process for photonic crystal materials.

Photonic Nanostructure Research Group
(‚P)Two-dimensional photonic crystal optical circuits on SOI substrate (line/point defects).
(‚Q)Three-dimensional photonic crystal structures and organic photonic crystal lasers.
(‚R)Interaction between photonic nanostructures and materials (negative refraction, extremely-large group velocity dispersion).

@Major results obtained this fiscal year 2001 are reported in the following pages.
@We have proposed fault-tolerant simple quantum protocol for bit-commitment that is unbreakable by individual particle attacks. This is a successful example to extend the basic idea of quantum cryptography, i.e., ultimate security guaranteed by uncertainty principle, to several magic protocols involving signature schemes, two-party secure computation, and so on.
@We demonstrated a cross-correlation technique for measuring an ultrashort soft x-ray-pulse shape using the rapid increase in Kr+ ion density caused by optical-field induced ionization. This technique can be a breakthrough to greatly improve the highest temporal resolution of 1 ps realized so far by x-ray streak cameras.
@Control of quantum mechanical superposition of an exciton in a single InGaAs quantum dot (QD) was demonstrated by irradiating successive optical pulses with precise delay-phase control. This demonstrates a phase rotation gate operation on the QD exciton as quantum bit and reinforces the potential of QD excitons in quantum logic application.
@We first fabricated efficient single-mode optical waveguides that operate within a photonic bandgap wavelength, embedded in the two-dimensional photonic crystals on SOI substrates. We have directly measured the dispersion of photonic crystal waveguides, and clarified that they have extremely large group dispersion. These results show promise for ultra-small, highly- functional optical integrated circuits based on photonic crystal structures.