Quantum Functional System Research Group

Principal Investigator

PI Name Seigo Tarucha
Degree D.Eng.
Title Group Director
Brief Resume
1978Staff member at the Basic Research Laboratories of Nippon Tel. & Tel. Corp.
1986Visiting Scientist , MPI (Stuttgart, Germany)(-1987)
1990Leader, Research Program on Electron Transport in Low-Dimensional Semiconductor Structures, NTT Basic Research Laboratories(-1998)
1993Distinguished member of technical staff, NTT Basic Research Laboratories (-1998)
1995Distinguished member of technical staff, NTT Basic Research Laboratories (-1998)
1998Professor, Department of Physics, University of Tokyo
2004Professor, Department of Applied Physics, University of Tokyo (-present)
2012Visiting Professor, Institut Néel CNRS, université Joseph Fourier(France)
2013Group Director, Quantum Functional System Research Group, Division Director, Quantum Information Electronics Division, RIKEN Center for Emergent Matter Science (-present)


We study hardware and underlying physics for quantum information processing with quantum control of solid-state quantum states. Quantum information processing is an ideal information technology whose operation accompanies low-energy dissipation and high information security. The purpose of our group is to demonstrate the ability of the solid-state information processing using quantum operations of quantum coherence and entanglement in semiconductor and superconductor nanostructures and finally outline a path for the realization. The specific research targets are "quantum computing" including quantum logic operation and quantum simulation, "quantum interface" which can offer quantum memory and relay, and "quantum nanodevices" relevant for the quantum control. We investigate architectures for best suited quantum systems, science and technology for both materials and devices, and fundamental physics of quantum entanglement, decoherence and spin correlation.

Research Fields

Physics, Engineering


Quantum computing
Quantum simulation
Quantum relay
Spin control
Quantum dots


A high-quality spin qubit in natural silicon

Quantum computers hold promise as next-generation computers that outperform conventional counterparts. Their building block, or the smallest unit of information, is called a qubit. It takes not only a conventional, binary value of 0 or 1, but also a superposition state of these. The problem is that its superposition state is very fragile against the noises. Therefore, qubits with sufficient qualities have only been realized in limited “ultra-clean” solid-state systems such as superconducting circuits and isotopically-purified silicon.

In this work, we demonstrate a high-quality qubit using a single electron spin in a quantum dot (Fig. A) on natural silicon. We improve the speed by about a hundred through device optimization, so that spin manipulation completes before influenced by noises. The operation fidelity reaches 99.6%, the highest value reported for natural-silicon-based qubits.

Our technique will allow qubit devices fabricated with the current semiconductor integration technology and thus form an important step towards the realization of large-scale quantum computing systems.

(Fig. A) A scanning electron micrograph of the quantum dot device fabricated on a natural silicon wafer.
(Fig. B) Randomized benchmarking results of single-qubit control fidelities.


Seigo Tarucha

Group Director tarucha[at]riken.jp R

Takashi Nakajima

Research Scientist

Jun Yoneda

Research Scientist

Hiroshi Kamata

Research Scientist

Kenta Takeda

Postdoctoral Researcher

Akito Noiri

Postdoctoral Researcher

Sen Li

Postdoctoral Researcher

Michael Desmond Fraser

Visiting Scientist

Tomohiro Otsuka

Visiting Scientist

Takumi Ito

Student Trainee

Yohei Kojima

Student Trainee



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