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Development of scalable silicon
quantum computer technology

News

Our advertisement feature was published on 29 February 2024, as part of Focal Point on Quantum computing in Japan in the online version of Nature, a weekly international journal publishing the finest peer-reviewed research in science and technology.


The advertisement feature can be found here: https://www.nature.com/articles/d42473-023-00437-6

Collections page: https://www.nature.com/collections/gieejcdceg

Moonshot Goal 6:
Realization of a fault-tolerant universal quantum computer that will revolutionize economy, industry, and security by 2050.

By 2025

 Develop fabrication techniques for scalable multi-qubit devices using high-quality silicon/silicon germanium (Si/SiGe) substrates and implement prototypes of small- to medium-scale quantum computers.

By about 2030

 We will develop fundamental fabrication technologies for multi-qubit devices that are compatible with the development of large-scale quantum computers in collaboration with industry.
 In parallel, we will characterize the multi-qubit devices and demonstrate the principle of high-fidelity quantum manipulation and phase error correction codes.

Members
Member Introductions

Project Managers

Seigo Tarucha

RIKEN
Center for Emergent Matter Science   Group Director
Center for Quantum Computing Team Leader

This project aims to develop scalable technologies for Silicon quantum computer. We will use sparse integration and medium-distance quantum coupling to implement a unit structure of qubits and scale up the qubit system by increasing the number of the unit structures.
 Based on this method we will develop fundamental technologies appropriate to implement large-scale quantum computers by 2030, and expand the technologies in cooperation with the semiconductor industry to implement universal quantum computers by 2050.

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Principal Investigators

R&D Themes 1-1: Development of Scalable Error Tolerant Si Quantum Bit Device Technology

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Takashi Nakajima

RIKEN
Center for Emergent Matter Science   Senior Scientist

We develop a silicon quantum processing unit utilizing a single electron spin as a qubit in lithographically defined quantum dot structures.
We aim to develop fundamental technologies for silicon-based fault tolerant quantum computing, including high-fidelity control of spin qubits and nano-fabrication of scaled-up qubit devices.

Project Members

Takashi Nakajima RIKEN Center for Emergent Matter Science Senior Scientist
Seigo Tarucha RIKEN Center for Emergent Matter Science
Center for Quantum Computing
Group Director
Team Leader
Kenta Takeda RIKEN Center for Emergent Matter Science Senior Scientist
Takashi Kobayashi RIKEN Center for Quantum Computing Research Scientist
Akito Noiri RIKEN Center for Emergent Matter Science Research Scientist
Leon Camenzind RIKEN Center for Emergent Matter Science Research Scientist
Ik Kyeong Jin RIKEN Center for Emergent Matter Science Postdoctoral Researcher
Wu Yi-Hsien RIKEN Center for Emergent Matter Science International Program Associate

R&D Themes 1-2: Development of Implementation Technology for Control Signal Routing in Integrated Si Qubits

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Takuji Miki

Kobe University
Graduate School of Science, Technology and Innovation   Associate Professor

We develop a signal routing implementation technology applicable to the control of a large number of silicon qubits. Utilizing semiconductor circuit techniques and advanced chip packaging technology, we focus on developing a multi-channel, high-resolution signal generator and constructing signal paths to improve the integrity by using silicon interposers and through silicon vias. This approach is expected to address the complexities and increased wiring density associated with a growing number of qubits, thereby enhancing the scalability of silicon quantum processors.

Project Members

Takuji Miki Kobe University Graduate School of Science, Technology and Innovation Associate Professor
Makoto Nagata Kobe University Graduate School of Science, Technology and Innovation Professor
Misato Taguchi Kobe University Graduate School of Science, Technology and Innovation Project Research Associate
Ryozo Takahashi Kobe University Graduate School of Science, Technology and Innovation Doctor Student
Ryuji Iwaisako Kobe University Graduate School of Science, Technology and Innovation Master Student
Kazuma Higashimomo Kobe University Graduate School of Science, Technology and Innovation Master Student

R&D Themes 2: Development of Middle-distance Quantum Link

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Takafumi Fujita

Osaka University
SANKEN   Associate Professor

 In our research, we are tackling the R & D of a middle-distance quantum information transfer. With this technology, it becomes possible to efficiently connect distant quantum bits.
 Our method uses voltage variations to transmit electron-spin quantum bits while maintaining the confinement of quantum dots. This allows for high-speed and reliable transmission of qubits. We plan to explore extending the transmission bus and adopting new methods to construct larger quantum systems and promote the integration of quantum bits.
 Our ultimate goal is to construct an on-chip quantum network, connecting high-performance, small-scale quantum processors, paving the way for advanced quantum computers.

Project Members

Takafumi Fujita Osaka University SANKEN Associate Professor
Rio Fukai Osaka University SANKEN Assistant Professor
Chinnasamy Rajkumar Osaka University SANKEN Specially Appointed Assistant Professor
Masayoshi Mori Osaka University SANKEN Specially Appointed Researcher
Hideaki Yuta Osaka University SANKEN Doctor Student
Tatsuo Tsuzuki Osaka University SANKEN Doctor Student
Kenichiro Senda Osaka University SANKEN Master Student
Alizadeh Ehsan Osaka University SANKEN Master Student
Naohiro Kida Osaka University SANKEN Master Student
Gen Nakagawa Osaka University SANKEN Master Student

R&D Themes 3: Development of Isotopically Controlled Si/SiGe Substrate Technology

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Satoru Miyamoto

Nagoya University
Graduate School of Engineering   Designated Associate Professor

 In order to achieve a scalable silicon quantum computer through the iterative implementation of elemental building blocks and mid-range quantum couplings, we develop an isotopically controlled Si/SiGe quantum platform to satisfy fault-tolerant requirements at the level of crystalline materials.
 In addition to implementation of ultra-high-quality Si isotope crystals with no scattering at the spatial scale of the qubit array units and quantum couplings, we promote development of atomic-scale interface control principles to mitigate the degradation of quantum controllability, and development of crystalline assessment schemes for isotopic substrates compatible with large-scale implementation.

Project Members

Satoru Miyamoto Nagoya University Graduate School of Engineering Designated Associate Professor
Yuki Yoneyama Nagoya University Graduate School of Engineering Master Student
Yukiko Kobayashi Nagoya University Graduate School of Engineering Technical Staff

R&D Themes 4-1: Picosecond Electron Wave Packet Generation and High-Fidelity Control of Electron Wave Packet Qubits

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Michihisa Yamamoto

RIKEN
Center for Emergent Matter Science   Team Leader

The University of Tokyo
Quantum-Phase Electronics Center, School of Engineering   Professor

We develop a quantum computer based on a new principle using electron wave packets propagating through quantum circuits.
A quantum bit is defined as a quantum state of an electron wave packet, and universal quantum operations are performed by repeatedly propagating the electron wave packet in a loop circuit where quantum operation circuits are embedded.This approach has the potential to construct a practical large-scale quantum computer with a small hardware realized using a single cryostat. The aim of this research item is to develop techniques for generating short electron wave packets of high quantum purity and high-fidelity quantum manipulation of qubits.

Project Members

Michihisa Yamamoto RIKEN
The University of Tokyo
Center for Emergent Matter Science
Quantum-Phase Electronics Center, School of Engineering
Team Leader
Professor
Naoki Ogawa RIKEN Center for Emergent Matter Science Team Leader
David Pomaranski The University of Tokyo Quantum-Phase Electronics Center, School of Engineering Assistant Professor
Tomonori Hashizume The University of Tokyo Quantum-Phase Electronics Center, School of Engineering Maseter Student

R&D Themes 4-2: Quantum Control and Readout of Microwave Electron Wave Packets

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Shintaro Takada

Osaka University
Graduate School of Science   Associate Professor

In this project, we will develop technologies to control the eigenstates of electron wave packets and to read out a single-electron wave packet as elemental technologies to realize a quantum computer based on a new principle using electron wave packets propagating in quantum circuits. The eigenstates of electron wave packets are usually controlled by controlling the width of the waveguide, but in this project, we will research and develop a new method using confinement of the electron wave packet in the direction of travel. In addition, we will develop a method to detect the presence or absence of electron wave packets by using electron spin qubits, which strongly interact with electron wave packets. We project the presence or absence of electron wave packets to the quantum state of electron spins. Then we detect electron wave packets by reading out the electro-spin state.

Project Members

Shintaro Takada Osaka University Graduate School of Science Associate Professor
Yunseong Jang Osaka University Graduate School of Science Master Student