RIKEN
National Institute of Advanced Industrial Science and Technology (AIST)
National Institute of Information and Communications Technology (NICT)
Osaka University
Fujitsu Limited
Nippon Telegraph and Telephone Corporation (NTT)Japanese joint research group launches quantum computing
cloud service
Opening access to Japan’s first superconducting quantum computerTokyo, March 24, 2023 – A consortium of joint research partners including RIKEN, theNational Institute of Advanced Industrial Science and Technology (AIST), the National
Institute of Information and Communications Technology (NICT), Osaka University,
Fujitsu Limited (Fujitsu) and Nippon Telegraph and Telephone Corporation (NTT)announced the successful development of Japan’s first superconducting(1) quantum
computer(2). Starting March 27, 2023, the partners will provide the newly developed
technology to users in Japan as a cloud service for non-commercial use under a joint
research agreement with RIKEN.
The new technology represents a significant step toward the wider use of quantum
computing in Japan.
The joint research group is comprised of: Dr. Yasunobu Nakamura, Director of the
RIKEN Center for Quantum Computing (RQC), Dr. Katsuya Kikuchi, Group Leader ofthe 3D Integration System Group of the Device Technology Research Institute at AIST,
Dr. Hirotaka Terai, Director of the Superconductive ICT Device Laboratory at the Kobe
Frontier Research Center of the Advanced ICT Research Institute of NICT, Dr.
Masahiro Kitagawa, Director of the Center for Quantum Information and Quantum
Biology at Osaka University, Dr. Shintaro Sato, Head of the Quantum Laboratory at
Fujitsu Research of Fujitsu, and Dr. Yuuki Tokunaga, Distinguished Researcher at NTT
Computer & Data Science Laboratories.

Superconducting quantum computer developed at RIKEN

Dawn of the Quantum Age: a new frontier in computing technology
Since the early twentieth century, quantum mechanics has been attracting attention as
a fundamental theory of physics, laying the foundation for the development of various
scientific fields. In particular, phenomena including quantum superposition and quantum
entanglement(3) have contributed significantly to the development of today’s science andtechnology. From the perspective of quantum information science, however, thepotential of quantum mechanics has not yet been fully exploited. Thus, R&D to apply
the fundamental principles of quantum mechanics to the technological fields ofcomputation, communications, and measurement have been gaining momentum
worldwide.
To further promote research in quantum information science, RIKEN established theMacroscopic Quantum Coherence Research Team under the lead of Dr. Jaw-ShenTsai(4) in 2001, and the RIKEN Center for Quantum Computing under the lead of Dr.
Yasunobu Nakamura in 2021, focusing on R&D in quantum computing. The Center for
Quantum Computing conducts R&D not only on superconducting quantum computer
hardware, but also on various physical systems including photonics research (led by
Dr. Akira Furusawa)(5), semiconductor methods (led by Dr. Seigo Tarucha)(6), andmethods using atoms in a vacuum. RIKEN is further promoting R&D in quantum
software including quantum computing theory, quantum algorithms and quantum
architecture, thus covering the entire spectrum of R&D in quantum computing.
In 2021, RIKEN and Fujitsu established the "RIKEN RQC-Fujitsu Collaboration Center"within the RQC. Research results were also utilized within the newly developed
superconducting quantum computer cloud service.
RIKEN and Fujitsu will further leverage their expertise in computing technologies andapplied quantum technology to provide a superconducting quantum computer forindustrial use by the end of FY 2023.
Research Methods and Results
The newly developed superconducting quantum computer uses integrated circuits with64 qubits(7) with two special features: two-dimensional integrated circuits andperpendicular wiring packages.
In the two-dimensional integrated circuits, four qubits are arrayed in a square, with eachconnected to its neighbors by inter-qubit connections (upper right of Fig. 1). In addition,
readout resonators and filter circuits for multiple readout are arranged in the square.
This basic unit consisting of four qubits can be arranged in two dimensions to form aqubit integrated circuit. The 64 qubit integrated circuit consists of 16 of these basic units
formed on a two centimeter square silicon chip. (Fig. 1)

Figure 1: 64 qubit integrated circuit chip
Left: 64 qubit two-dimensional integrated circuit chip performs quantum computation. The
design has 16 basic units, each comprised of 4 qubits. The titanium nitride film, which is asuperconductor, gives off a gold shine.
Upper right: schematic diagram of a basic unit of 4 qubits. Qubits are arranged at the four
corners of a square, and a readout circuit designed in the middle.
Lower right: electron micrograph of a Josephson junction forming a qubit.

Furthermore, if the wiring is on the same planar surface as the qubits in the system, thespace of the wiring to the outside is insufficient for the number of qubits arrayed in thechip, so it is necessary to devise methods to control individual qubits and wiring forreadout. Therefore, the joint research group adopted a design based on perpendicularwiring packages, in which the wiring to the chip for the qubits arrayed on a twodimensional planar surface is perpendicularly connected. The research team is further
developing a wiring package that enables the wiring to the qubit integrated circuit chip at
once (Fig. 2).
Taking advantage of the features of the two-dimensional integrated circuits andperpendicular wiring packages, a highly scalable system is formed in which the numberof qubits can be easily increased. This enables the large-scale of the newly developed
system without altering the basic design.

Figure 2: Perpendicular wiring packages

Left: schematic diagram of perpendicular wiring. The control and readout wiring for the qubits isperpendicularly connected to the chip via a contact probe for signals. Microwave signals aretransmitted and received through the wiring.
Right: wiring package for the qubit integrated circuit chip.

The signals controlling the qubits use voltage pulses that oscillate at microwave
frequencies (8-9 GHz). However, as each qubit requires a different microwave
frequency, the joint research group developed a controller that can generate stablemicrowave phases with high precision (Fig. 3). The team also developed software forthe controller that controls the qubits.

Figure 3: Qubit controller
Qubit controller consisting of an oscillator and receiver for microwave signals. The new 64 qubit
quantum computer uses 96 input wires and 16 output wires for control and readouts to perform
quantum calculations.

Starting March 27, 2023, RIKEN is providing the newly developed superconducting
quantum computing technology as a “quantum computing cloud service” (Fig. 4) for
non-commercial use to researchers and engineers in Japan under joint research
agreements. Users will be able to access the new superconducting quantum computerfor jobs within the scope of the joint research agreement and can send data/receive
results via the cloud.

Figure 4: Image of user access to superconducting quantum computer
Authentication of registered users and job transmission/reception on a web interface.

Moving forward, the joint research group will further enhance the new system to enable
quantum computing operations with a higher number of qubits and increase the densityof wiring inside the dilution refrigerator (Fig. 5). The research team will further provide
access to the superconducting quantum computer as a testbed for noisy intermediatescale quantum (NISQ) computers (8).
Based on the newly developed services, the research partners will further accelerate
R&D in quantum computing through deeper collaboration with quantum softwaredevelopers, quantum computing researchers, and corporate developers.

Figure 5: Wiring inside the dilution refrigerator of the 64 qubit superconducting quantum
computer
A 64 qubit integrated circuit chip is placed in a central cylindrical magnetic shield to connect
control and readout wiring. In operations, it is necessary to cool the periphery of the chip toabout 10 mK (about -273 °C), so the entire chip is placed in a vacuum insulated container andcooled by a dilution refrigerator.

Future plans
Using the highly scalable integrated circuit (Fig. 6) as a core technology, the joint
research team will continue to work toward the realization of quantum computers with
100 and 1,000 qubits, and promote further R&D toward the integration of 1 million qubits
and the realization of fault-tolerant quantum computing (9) for real world application.

Figure 6: Future image of qubit integrated circuits
By periodically arranging basic units composed of four qubits on a planar surface, thenumber of integrated qubits can be increased. The figure above shows the future image of
1,024 qubits by periodically arranging 64 qubits in a 4 x 4 array.

Joint Research Group Members
RIKEN Center for Quantum Computing
Yasunobu Nakamura, Ph.D., Director(Team Leader of the Superconducting Quantum Electronics Research Team)
Shinichi Yorozu, Ph.D. Deputy Director
Superconducting Quantum Electronics Research Team
Shuhei Tamate, Ph.D., Research Scientist
Koichi Kusuyama, Ph.D., Senior Technical Staff
Superconducting Quantum Electronics Joint Research Unit
Eisuke Abe, D.Sc., Unit Leader
Superconducting Quantum Computing System Research Unit
Yutaka Tabuchi, Ph.D., Unit Leader
3D Integration System Group of the Device Technology Research Institute at the
National Institute of Advanced Industrial Science and Technology (AIST)
Katsuya Kikuchi, Ph.D., Group Leader
Superconductive ICT Device Laboratory at the Kobe Frontier Research Center ofthe Advanced ICT Research Institute of the National Institute of Information andCommunications Technology (NICT)
Hirotaka Terai, Ph.D., Director
Yuji Hishida, Ph.D., Fixed Term Research Engineer
Center for Quantum Information and Quantum Biology at Osaka University
Masahiro Kitagawa, Ph.D., Director and Professor

(Professor, Graduate School of Engineering Science)
Keisuke Fujii, Ph.D., Deputy Director and Professor(Professor, Graduate School of Engineering Science/Team Leader, Quantum
Computing Theory Research Team, RIKEN Center for Quantum Computing)
Makoto Negoro, Ph.D., Deputy Director and Associate Professor
Takefumi Miyoshi, Ph.D., Specially Appointed Associate Professor(Director, e-trees.Japan, Inc.)
Shunsuke Saruwatari, Ph.D., Associate Professor(Associate Professor, Graduate School of Information Science and Technology)
Naoyuki Masumoto, Ph.D., Specially Appointed Researcher
Quantum Laboratory at Fujitsu Research of Fujitsu Limited
Shintaro Sato, Ph.D., Head of Quantum Laboratory
NTT Computer & Data Science Laboratories
Yuuki Tokunaga, Ph.D., Distinguished Researcher
Yasunari Suzuki, Ph.D., Researcher
Research Support
This research received funding support from the Quantum Leap Flagship Program (QLEAP) of the Ministry of Education, Culture, Sports, Science and Technology “R&D of
Superconducting Quantum Computer (Research Representative: Yasunobu Nakamura)
Grant No. JPMXS0118068682” (RIKEN, Osaka University, Fujitsu Limited, Nippon
Telegraph and Telephone Corporation, the University of Tokyo, Tokyo Medical and
Dental University, Tohoku University, National Institute of Advanced Industrial Scienceand Technology, National Institute of Information and Communications Technology.
Toshiba Corporation, Mitsubishi Electric Corporation, NEC Corporation, QunaSys Inc.),“Development of quantum software by intelligent quantum system design and its
applications (Research Representative: Keisuke Fujii) Grant no. JPMXS0120319794”(Osaka University, Keio University, Nagoya University, University of Tokyo, Kyoto
University, Nippon Telegraph and Telephone Corporation, e-trees.Japan, Inc.), The
Japan Science and Technology Agency, Exploratory Research for Advanced
Technology (ERATO) “NAKAMURA Macroscopic Quantum Machines Project (Research
Coordinator: Yasunobu Nakamura),” and COI-NEXT program “Quantum Software
Innovation Hub (Project Leader: Masahiro Kitagawa).”

(From left): Eisuke Abe, Yasunobu Nakamura, and Yutaka Tabuchi
Notes
1. Superconducting method:
A quantum computer system that uses a Josephson junction, a tunnel junction
element, to realize quantum bits on an electronic circuit using a superconducting
material. Because of the small scale of the energy difference of the 0 or 1 qubit
state, it is necessary to cool the qubits to extremely low temperatures (to about 273°C) in a dilution refrigerator.
2.

Quantum computers:
Computers performing calculation based on the principles of quantum physics. By
using quantum superposition and quantum entanglement that are not possible withconventional computers, quantum computers are expected to solve a variety ofproblems at high speed, including prime factorization or efficient simulations ofquantum-like behavior such as the electronic state in molecules.

3.

Quantum superposition and quantum entanglement:
A phenomenon where multiple states exist at the same time, which is incompatible
with how humans experience the world. Quantum entanglement is a uniquecorrelation in quantum physics that occurs in combination with quantum
superposition.

4. Dr. Jaw-Shen Tsai:
Currently Team Leader of the Superconducting Quantum Simulation Research
Team at the RIKEN Center for Quantum Computing
5. Dr. Akira Furusawa:
Deputy Director of the Center for Quantum Computing and Team Leader of the
Optical Quantum Computing Research Team6. Dr. Seigo Tarucha:
Team Leader, Semiconductor Quantum Information Device Research Team
7. Qubits:
The smallest unit of quantum information. In a regular digital circuit, a bit can be in
one of two states, either 0 or 1, but a qubit can be in a superposition state of 0 and
1. It can superimpose 0 and 1 for any complex numbers, and the state of a qubit
schematically can be shown by an arrow displaying an arbitrary point from thecenter of a sphere to the surface of the sphere.
8. Noisy intermediate-scale quantum (NISQ) computer:
Small or medium-sized quantum computers in which computing errors generated bynoise cannot be corrected. Applications such as variational quantum algorithms are
expected for practical use in the near future.
9. Fault-tolerant quantum computing:
Conventional computers also cause errors, but they have the ability to correct errors
in the middle of calculations. In the case of quantum computers, likewise,
calculations can be conducted while correcting quantum errors. By generating
quantum entanglement between multiple qubits, the information of one qubit isexpressed, and by detecting the turbulence between entangled qubits, errors canbe corrected without disturbing the quantum information. Fault-tolerant quantum
computation means quantum computation that reduces the probability of errors
occurring in the control and readout of quantum bits throughout a quantum
computer, and has the ability to perform large-scale calculations while correcting
errors occurring in the process of computation without accumulating the effects oferrors. It is estimated that 1 to 100 million qubits are necessary for fault-tolerant
quantum computing.
About RIKEN
RIKEN is Japan's largest comprehensive research institution renowned for high-quality
research in a diverse range of scientific disciplines. Founded in 1917 as a private
research foundation in Tokyo, RIKEN has grown rapidly in size and scope, today
encompassing a network of world-class research centers and institutes across Japan.
https://www.riken.jp/en/about/
About National Institute of Advanced Industrial Science and Technology (AIST)
AIST is one of the largest public research organizations in Japan and has a history of
more than 140 years. AIST focuses on the creation and practical realization oftechnologies useful in Japanese industry and society, working to bridge gaps between
innovative technological seeds and commercialization. As a pioneer and still core player
in Japan’s national innovation system, AIST manages some 2,300 specialists engaged
in research and development at 11 research bases across the country.
https://www.aist.go.jp/index_en.html

About National Institute of Information and Communications Technology (NICT)As Japan’s sole National Research and Development Agency specializing in the field of
information and communications technology, NICT is charged with promoting ICT sector
as well as research and development in ICT, which drives economic growth and creates
an affluent, safe and secure society.
For more information, please visit https://www.nict.go.jp/en/.
About Osaka University
Osaka University was founded in 1931 as one of the seven imperial universities ofJapan and is now one of Japan's leading comprehensive universities with a broad
disciplinary spectrum. This strength is coupled with a singular drive for innovation that
extends throughout the scientific process, from fundamental research to the creation of
applied technology with positive economic impacts. Its commitment to innovation has
been recognized in Japan and around the world, being named Japan's most innovative
university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in
the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now,
Osaka University is leveraging its role as a Designated National University Corporation
selected by the Ministry of Education, Culture, Sports, Science and Technology tocontribute to innovation for human welfare, sustainable development of society, andsocial transformation.
Website: https://resou.osaka-u.ac.jp/en
About Fujitsu
Fujitsu’s purpose is to make the world more sustainable by building trust in society
through innovation. As the digital transformation partner of choice for customers in over
100 countries, our 124,000 employees work to resolve some of the greatest challenges
facing humanity. Our range of services and solutions draw on five key technologies:
Computing, Networks, AI, Data & Security, and Converging Technologies, which webring together to deliver sustainability transformation. Fujitsu Limited (TSE:6702)
reported consolidated revenues of 3.6 trillion yen (US$32 billion) for the fiscal year
ended March 31, 2022 and remains the top digital services company in Japan bymarket share. Find out more: www.fujitsu.com/
About Nippon Telegraph and Telephone Corporation (NTT)NTT believes in resolving societal issues through our business operations by applying
technology for good. We help clients accelerate growth and innovate for current andnew business models. Our services include digital business consulting, technology andmanaged services for cybersecurity, applications, workplace, cloud, datacenter andnetworks all supported by our deep industry expertise and innovation. As a top 5 global
technology and business solutions provider, our diverse teams operate in 80+ countries
and regions and deliver services to over 190 of them. We serve over 80% of Fortune
Global 100 companies and thousands of other clients and communities around theworld. For more information on NTT, visit www.global.ntt/.

Press Contacts
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