Quantum Effect Device Research Team

Principal Investigator

PI Name Koji Ishibashi
Degree D.Eng.
Title Team Leader
Brief Resume
1988D.Eng., Graduate School of Electrical Engineering, Osaka University
1988Researcher, Frontier Research Program, RIKEN
1991Researcher, Semiconductor Laboratory, RIKEN
1996Visiting Researcher, Delft University of Technology, The Netherlands (until 1997)
2003Chief Scientist, Advanced Device Laboratory, RIKEN (-present)
2003Adjunct Professor, Chiba University (-present)
2005Adjunct Professor, Tokyo University of Science (-present)
2008Adjunct Professor, Tokyo Institute of Technology (-present)
2013Team Leader, Quantum Effect Device Research Team, Quantum Information Electronics Division, RIKEN Center for Emergent Matter Science (-present)
2016Visiting Professor, Universiti Teknologi Malaysia (-present)
2017Visiting Professor, Osaka University (-present)


We study quantum effects that appear in nanoscale structures and apply them to functional nanodeives. Nanomaterials that are formed in a self-assemble manner, such as carbon nanotubes, graphene and semiconductor nanowires (Si/Ge, InAs, InSb) are used as building blocks for extremely small nanostructures, and are combined with top-down nanofabrication to fabricate functional nanodevices with a sub-10nm scale. We focus on hybrid nanostructures, such as carbon nanotube/molecule heterostructures and topological insulator or nanostructures/superconductor hybrid nanostructures, to realize unique functionalities that enable us to control electrons, photons, excitons, cooper pairs and plasmons on a single quantum level. With those, we develop single electron devices and circuits, quantum information devices, plasmonic and photovoltaic devices for future low-power nanoelectronics.

Research Fields

Engineering, Physics


Carbon nanotube
Semiconductor nanowire
Quantum dots
Topological superconductor
Quantum information devices


Towards hybrid quantum information devices with quantum dots in a microwave resonator

We study quantum dots interacting with microwave photons in a superconducting coplanar waveguide resonator for the future hybrid quantum information devices. The quantum dot, or an artificial atom in other words, can realize a large electron-photon interaction at a single quanta level simply because the size of the artificial atom is much larger than natural atoms. Then, entanglement between an electron and a photon would be possible, a key requirement for quantum information processing. The single spin-photon interaction is also being explored with a help of a spin-orbit interaction (SOI). We use InSb or Ge/Si nanowire quantum dots that have a large SOI and are placed in a resonator (see fig). The double dot is formed by applying gate voltages on the finger gates underneath the nanowire. We measure microwave transmission at low temperatures (~100mK), and study resonant characteristics that are affected by microscopic charge (or spin) states of the double quantum dot. At this moment, we observe an charge-photon interaction with less than single photon in a resonator, but have not succeeded in realizing coherent interaction because of a large decoherence in the quantum dot.

Scanning electron microscope image of the Ge/Si nanowire quantum dots embedded in a superconducting coplanar waveguide resonator.


Koji Ishibashi

Team Leader kishiba[at]riken.jp R

Keiji Ono

Senior Research Scientist

Russell Stewart Deacon

Senior Research Scientist

Daichi Suzuki

Special Postdoctoral Researcher

Hui Wang

Postdoctoral Researcher



2-1 Hirosawa, Wako, Saitama 351-0198 Japan