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Kosaka-Sekiguchi Lab
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The lab uses diamond to connect quantum computers with quantum communication.
AboutAbout the lab
Connecting quantum computers and communication at the quantum level.
The Kosaka-Sekiguchi Lab conducts research toward quantum repeaters, quantum computers, and a quantum internet that connects them through quantum communication.
When impurities such as nitrogen are added to diamond and the diamond is heat-treated, color centers called nitrogen-vacancy (NV) centers form, and they function as memory that stores quantum states.
The lab has succeeded in a proof-of-principle demonstration of a quantum repeater based on quantum teleportation using diamond, and continues its research toward a quantum internet.
The lab's website presents it under the name "Kosaka Lab."
Key terms
- Quantum repeater
- A mechanism needed to extend the distance of quantum cryptographic communication, which is limited by optical fiber loss.
- Nitrogen-vacancy (NV) center
- A type of color center formed by adding nitrogen to diamond. It functions as a quantum memory.
- Quantum transducer
- A device that transfers quantum information between superconducting qubits (microwaves) and optical communication without degrading it.
- Quantum memory
- A device that holds quantum states for a long time and can freely generate quantum entanglement with photons.
NewsLab news
New paper "Absorption-emission quantum repeater using diamond quantum memories" released
Prof. Kosaka was elected a Fellow of the Japan Society of Applied Physics (20th class, FY2026)
Students received numerous awards upon completing their master's programs
A master's student received the Best Presentation Award at the 21st Nanotech Exchange Symposium
A paper on microwave resonators made of superconducting nanowires was published in Physical Review Letters
ResearchResearch themes
The research is based on the idea of connecting quantum computers and quantum communication at the quantum level, rather than treating them separately, so that computation and information processing are carried out across the whole network. With quantum interfaces, quantum computers, and long-distance quantum repeaters as the main elements, the lab works on the quantum memory and quantum operations (control and readout) that support them.
*Illustrative imageInterfaces Connecting Quantum Communication and Computation
This is the technology that maps quantum information carried by photons onto the internal states of a quantum node, and converts it back into light. Realizing a quantum transducer that links superconducting qubits with optical communication is regarded as an essential challenge for distributed quantum computing.
*Illustrative imageDistributed and Fault-Tolerant Quantum Computing
With quantum computers operating as part of a network in mind, the lab focuses on computing platforms including superconducting quantum computers. It treats interfaces, quantum memory, and control as a single, integrated problem.
*Illustrative imageColor Centers in Diamond (NV Centers)
Because quantum systems must hold quantum states for a relatively long time, couple to light, and be precisely controlled and read out, the lab uses nitrogen-vacancy (NV) centers. It positions them as the physical system for realizing quantum interfaces, quantum memory, and operations within a node.
*Illustrative imageQuantum Repeaters to Extend the Range of Quantum Cryptographic Communication
To overcome the distance limit that optical fiber loss places on quantum cryptographic communication, the lab is building up the elemental technologies of quantum repeaters step by step, using color centers in diamond with quantum memory and quantum operations at the core.
MembersFaculty
The members of the Kosaka-Sekiguchi Lab consist of faculty, project faculty, part-time faculty, doctoral, master's, and undergraduate students, technical assistants, administrative assistants (secretaries), and QIC-affiliated researchers.As of 2026
- ProfessorHideo Kosaka
- Assistant ProfessorYuhei Sekiguchi
- Specially Appointed Faculty (Assistant Professor)Akira Kamimaki
- Specially Appointed Faculty (Assistant Professor)Akiyuki Konno
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Alice in BBN laboratory - DARPA Quantum Network, January 2003” Daderot / CC0 (cropped)
- Interfaces Connecting Quantum Communication and Computation: “Entangled link - Barb - DARPA Quantum Network - P1010012” Daderot / CC0 (cropped)
- Distributed and Fault-Tolerant Quantum Computing: “Quantum-computer-Chalmers 2017” Anita Fors (Chalmers) / CC BY-SA 4.0 (cropped)
- Color Centers in Diamond (NV Centers): “Diamond (side view)” Pavel.Somov / CC BY 4.0 (cropped)
- Quantum Repeaters to Extend the Range of Quantum Cryptographic Communication: “Quantum Entanglement Experiment via Spontaneous Parametric Down-Conversion (SPDC)” Farbodk / CC BY-SA 4.0 (cropped)
- Related lab (Horikiri-Ozawa Lab): “Full wafer of Intel quantum computers” Steve Jurvetson from Menlo Park, USA / CC BY 2.0 (cropped)
- Related lab (Hong-Akamatsu-Asakawa Lab): “Optical atomic clock ( )” National Institute of Standards and Technology / Public domain (cropped)
- Related lab (Ohno (Shinya) Lab): “Atomic Force Microscope 02” Gannu03 / CC BY-SA 4.0 (cropped)
- Related lab (Shuto Lab): “PES Hemispherical Analyzer With Electrons And Signs” Ichwarsnur / CC BY-SA 4.0 (cropped)
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