- Associate Professor, Department of Information and Communications Engineering, Institute of Science Tokyo
- Research Interests: Quantum Error Correction, Coding Theory, Information Theory
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The parity-check matrices used in our recent studies are available upon reasonable request. Please feel free to contact us if you are interested.My recent research focuses on quantum error correction using low-density parity-check (LDPC) codes, particularly the construction and decoding of Calderbank-Shor-Steane (CSS) quantum codes based on sparse binary or non-binary matrices. We aim to design quantum codes that approach the hashing bound under practical decoding algorithms.
One of our major achievements is the development of explicit quantum LDPC codes constructed from permutation matrices, which demonstrate excellent error-correcting performance over depolarizing channels. These constructions are designed to avoid short cycles in the Tanner graph to suppress the error floor phenomenon.
We are also working on decoding algorithms that handle degeneracy in quantum noise models, including syndrome-based decoding and belief propagation methods adapted for Galois fields. Recent results suggest that combining dual codes with appropriate post-processing significantly improves the decoding success rate.
This line of work contributes to the long-term goal of realizing scalable and fault-tolerant quantum communication and computation.
Our new preprint titled "Quantum Error Correction Exploiting Degeneracy to Approach the Hashing Bound" is now available on arXiv.
This work presents a decoding algorithm that explicitly exploits the degeneracy of quantum errors under the depolarizing channel. Using non-binary LDPC codes and syndrome-based methods, the proposed decoder achieves a frame error rate of $10^{-4}$ at a physical error rate of 9.45% with a code of 104,000 logical qubits and 312,000 physical qubits, approaching the quantum hashing bound.
The following paper and poster presentations have been accepted to ISTC 2025 (13th International Symposium on Topics in Coding), which will be held in Los Angeles, USA, in August 2025.
The regular paper presents a novel construction of quantum APM-LDPC codes using non-circulant affine permutation matrices, demonstrating the feasibility of girth-16 code design beyond the conventional constraints of quantum QC-LDPC codes. The poster presentations provide an overview of recent developments in quantum error correction using non-binary LDPC codes and future directions for high-girth code constructions.
Prof. Kenta Kasai (Tokyo University of Science and Technology) will present his poster titled “Perspectives on Degeneracy and Structure in Non-Binary LDPC Code-Based QEC” at the ISIT 2025 workshop “Quantum Information – Open Problems, Impact, and Challenges (Q-PIC)”.
The workshop focuses on key challenges and open problems in quantum information science, and the poster highlights new perspectives on degeneracy and structural properties in quantum error correction based on non-binary LDPC codes.
The poster will be on display starting at 9:30 AM on June 24, 2025 (Tuesday) at the Rackham Graduate School, University of Michigan. Prof. Kasai will also deliver a 30-second pitch talk and be available for Q&A sessions.
For more details, please visit the Q-PIC workshop page.
Prof. Kenta Kasai (Institute of Science Tokyo) will present his recent work titled “Follow-Up Study on Efficient Mitigation of Error Floors in Quantum Error Correction using Non-Binary LDPC Codes” at the Recent Results Poster Session of the IEEE International Symposium on Information Theory (ISIT) 2025.
The session will take place on Monday, June 23, 2025, from 14:30 to 15:50 at the ballroom of the Michigan League in Ann Arbor.
This follow-up study builds upon previously proposed techniques to mitigate error floors in quantum LDPC codes and evaluates their performance and practicality in greater depth.
The poster "Towards Practical Quantum Error Correction: Near-Optimal Performance and Floor Mitigation via Non-Binary LDPC Codes", authored by Kenta Kasai, has been accepted for presentation at the Quantum Error Correction (QEC25) conference.
This work addresses the suppression of error floors in quantum LDPC codes and demonstrates near-optimal performance using non-binary belief propagation decoding.
The acceptance rate for this year’s poster session was below 40%, making it a highly competitive venue for recent results in quantum error correction.
More details available on the QEC25 website.
The paper "Efficient Mitigation of Error Floors in Quantum Error Correction using Non-Binary Low-Density Parity-Check Codes", authored by Kenta Kasai, has been accepted for presentation at the IEEE International Symposium on Information Theory (ISIT 2025).
This paper presents decoding algorithms designed to mitigate the error floor in quantum LDPC codes constructed over non-binary fields, achieving performance close to the hashing bound under practical quantum noise models.
As a follow-up to this work, we will present new results in the Recent Results Poster Session at ISIT 2025, to be held in Ann Arbor, Michigan.
Preprint available on arXiv.
Email: kenta@ict.eng.isct.ac.jp
Office: Room 418, South Building 3, Ookayama Campus, Institute of Science and Technology
2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan