Program

Program

プログラム Workshop program

Day 1 (12/17)
13:20–13:30 Opening Remarks
13:30–15:00 Tutorial Lecture 1 (90 min) Speaker:  Hayato  Goto
15:00–15:30 Break (30 min)
15:30–17:00 Tutorial Lecture 2 (90 min) Speaker: Hayata Yamasaki

Day 2 (12/18)
10:00–10:40 Invited Talk 1 Speaker: Thomas Scruby
10:40–11:20 Invited Talk 2 Speaker: Shiro Tamiya
11:20–12:00 Invited Talk 3 Speaker: Junichi Haruna
12:00–13:30 Lunch break (90 min)
13:30–14:10 Invited Talk 4 Speaker: Yasunari Suzuki
14:10–14:50 Invited Talk 5 Speaker:  Ilkwon Byun
14:50–15:30 Break (40 min)
15:30–16:10 Invited Talk 6 Speaker: Oliver Hahn
16:10–16:50 Invited Talk 7 Speaker: Takaya Matsuura
16:50–17:00 Break (10 min)
17:00–18:30 Poster session

Day 3  (12/19)
10:00–10:40 Invited Talk 8 Speaker: Kenta Kasai
10:40–11:20 Invited Talk 9 Speaker: Nicholas Connolly
11:20–12:00 Invited Talk 10 Speaker: Manabu Hagiwara
Afternoon: Free eiscussion

Titles and  Abstracts

Day 1

Tutorial Lecture 1

Hayato Goto (RIKEN)

Title: Tutorial for QEC and FTQC with CSS codes 

Abstract: Most quantum error-correcting codes used for fault-tolerant quantum computing (FTQC) are so-called CSS codes (stabilizer codes only with Z-type and X-type stabilizer generators). In this tutorial talk, I'll present the basics of quantum error correction (QEC) and FTQC with representative CSS codes.

Tutorial Lecture 2

Hayata Yamasaki (U. Tokyo)

Title: Tutorial for surface code and quantum low-density parity-check code

Abstract: I will present the basics of quantum error correction and fault-tolerant quantum computation with the surface code and the quantum low-density parity-check (QLDPC) code.

Day 2

Invited Talk 1

Thomas Scruby (OIST)

Title: High-threshold, low-overhead and single-shot decodable fault-tolerant quantum memory 

Abstract: We present a new family of quantum low-density parity-check codes, which we call radial codes, obtained from the lifted product of a specific subset of classical quasi-cyclic codes. The codes are defined using a pair of integers (r, s) and have parameters [[2r^2s, 2(r − 1)^2, ≤2s]], with numerical studies suggesting average-case distance linear in s. In simulations of circuit-level noise, we observe comparable error suppression to surface codes of similar distance while using approximately five times fewer physical qubits. This is true even when radial codes are decoded using a single-shot approach, which can allow for faster logical clock speeds and reduced decoding complexity. We describe an intuitive visual representation, canonical basis of logical operators and optimal-length stabiliser measurement circuits for these codes, and argue that their error correction capabilities, tunable parameters and small size make them promising candidates for implementation on near-term quantum devices.

Invited Talk 2

Shiro Tamiya (nanoQT)

Title: Fault-tolerant quantum computation with polylogarithmic time and constant space overheads

Abstract: A major challenge in fault-tolerant quantum computation is to reduce both the space overhead, that is, the large number of physical qubits per logical qubit, and the time overhead, that is, the long physical gate sequences needed to implement a logical gate. Minimizing these overheads is essential for the realization of scalable fault-tolerant quantum computation. Here we prove that a protocol using non-vanishing-rate quantum low-density parity-check (QLDPC) codes, combined with concatenated Steane codes, achieves constant space overhead and polylogarithmic time overhead, even when accounting for the required classical processing. This protocol offers an improvement over existing constant-space-overhead protocols. With this approach, we resolve a logical gap in the existing arguments for the threshold theorem for the constant-space-overhead protocol with QLDPC codes and complete its proof. This provides a theoretical foundation to guide the development of scalable, resource-efficient quantum computers.

Invited Talk 3

Junichi Haruna (Osaka U.)

Title: Logical Gates by Gauge Field Formalism of Quantum Error Correction 

Abstract: The gauge field formalism, or operator-valued cochain formalism, has recently emerged as a powerful framework for describing quantum Calderbank-Shor-Steane (CSS) codes. In this work, we extend this framework to construct a broad class of logical gates for general CSS codes, including the S, Hadamard, T, and (multi-)controlled-Z gates, under the condition where fault-tolerance or circuit-depth optimality is not necessarily imposed. We show that these logical gates can be expressed as exponential of polynomial functions of the electric and magnetic gauge fields, which allows us to derive explicit decompositions into physical gates. We further prove that their logical action depends only on the (co)homology classes of the corresponding logical qubits, establishing consistency as logical operations. Our results provide a systematic method for formulating logical gates for general CSS codes, offering new insights into the interplay between quantum error correction, algebraic topology, and quantum field theory. This talk is based on arXiv:2511.15224. 

Invited Talk 4

Yasunari Suzuki (RIKEN)

Title: Efficient FTQC designs based on properties of quantum programs  

Abstract: Proposing an efficient design for fault-tolerant quantum computing (FTQC) is a major challenge, as the number of available qubits and their quality are limited. In classical computing, modern architectures exploit common properties of typical programs, such as access locality, to achieve resource-efficient designs without compromising performance. In contrast, FTQC machines are generally designed to execute arbitrary quantum programs and do not explicitly discuss or leverage such properties. In this talk, I will present our recent results on efficient FTQC designs based on a detailed analysis of state-of-the-art quantum algorithms with exponential speedups. I will demonstrate that the ideas inspired from modern computer architectures, such as load-store architecture and switching network, can significantly reduce hardware requirements for large-scale distributed FTQC.

 Invited Talk 5

Ilkwon Byun (Kyushu U.)

Title: Toward Practical Quantum Computer Systems: A Computer Architect’s Perspective

Abstract: Quantum computing is a new paradigm with significant potential to solve many classically intractable problems. However, practical quantum computing requires hundreds of fault-tolerant logical qubits, each built with hundreds of noisy physical qubits via quantum error correction (QEC). This talk introduces the computer architect's approach to developing a practical fault-tolerant quantum computer system: full-system quantum computer modeling. As a concrete example, we present our research on designing a million-qubit control system for superconducting quantum computers. This talk will conclude with a discussion of how computer architects will respond to the rapidly advancing field of quantum computing.

 Invited Talk 6

Oliver Hahn (U. Tokyo)

Title: Non-Gaussian Quantum Resources: Quantification and Computation 

Abstract: Non-Gaussianity is a necessary resource not only for universal quantum computation but also for enabling error correction in continuous-variable (CV) systems. In this talk, I will summarize the role of non-Gaussianity in CV quantum computing and present several approaches to quantifying it. I will then discuss how the classical simulation cost of such a system scales with the amount of non-Gaussianity. At the end, I will present the connection between non-Gaussianity and quantum magic using Gottesman–Kitaev–Preskill codes, which provides techniques for both continuous and discrete-variable systems.

Invited Talk 7

Takaya Matsuura (Osaka U.)

Title:  Fault-Tolerance of Continuous-Variable Quantum Computation

Abstract: Continuous-variable (CV) systems are acquiring growing interest as candidates for implementing quantum computation, and among many CV quantum error-correcting codes, the Gottesman-Kitaev-Preskill (GKP) code is particularly suitable for optical CV quantum computing. However, the fault tolerance of CV quantum computation based on the GKP code was proved only against very specific noise models. In this work, we prove the fault tolerance of CV quantum computation based on the GKP code under a general type of noise models, namely, independent Markovian noise models. This is a first step towards a comprehensive understanding of the fault-tolerant quantum information processing in CV systems.

 Invited Talk 8

Kenta Kasai (Science Tokyo)

Title: 

Abstract: 

 Invited Talk 9

Nicholas Connolly (OIST)

Title:  A Brief Overview of some Quantum Erasure Decoding Algorithms 

Abstract: The erasure-channel is one of the simplest error models, wherein a transmitted bit (or qubit) is lost with some probability. This model has significant practical interest given that, for many communication scenarios such as photonic systems, erasures are the dominant type of error. The goal of erasure correction is to recover a corrupted message using the partial information received, with the additional assumption that non-erased bits have no errors. In this talk, we will review a handful of quantum erasure decoding algorithms, beginning with a generalization of a simple classical algorithm known as the peeling decoder.

 Invited Talk 10

Manabu Hagiwara (Chiba U.)

Title: The first thing you should learn when studying error correction 

Abstract: Error-correcting codes are foundational tools across many scientific disciplines. This talk will introduce the essential concepts needed to begin studying error correction. By exploring the breadth of coding theory, I hope attendees will be inspired to delve deeper into the field. Toward the end of the lecture, I will present recent developments in quantum deletion error-correcting codes that I have developed, along with future directions for research.