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Paper 1

Low Latency GNN Accelerator for Quantum Error Correction

Alessio Cicero, Luigi Altamura, Moritz Lange, Mats Granath, Pedro Trancoso

Year

2026

Journal

arXiv preprint

DOI

arXiv:2603.22149

arXiv

2603.22149

Quantum computers have the potential to solve certain complex problems in a much more efficient way than classical computers. Nevertheless, current quantum computer implementations are limited by high physical error rates. This issue is addressed by Quantum Error Correction (QEC) codes, which use multiple physical qubits to form a logical qubit to achieve a lower logical error rate, with the surface code being one of the most commonly used. The most time-critical step in this process is interpreting the measurements of the physical qubits to determine which errors have most likely occurred - a task called decoding. Consequently, the main challenge for QEC is to achieve error correction with high accuracy within the tight $1μs$ decoding time budget imposed by superconducting qubits. State-of-the-art QEC approaches trade accuracy for latency. In this work, we propose an FPGA accelerator for a Neural Network based decoder as a way to achieve a lower logical error rate than current methods within the tight time constraint, for code distance up to d=7. We achieved this goal by applying different hardware-aware optimizations to a high-accuracy GNN-based decoder. In addition, we propose several accelerator optimizations leading to the FPGA-based decoder achieving a latency smaller than $1μs$, with a lower error rate compared to the state-of-the-art.

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Paper 2

Quasi-Majorana modes in the $p$-wave Kitaev chains on a square lattice

S. Srinidhi, Aayushi Agrawal, Jayendra N. Bandyopadhyay

Year

2024

Journal

arXiv preprint

DOI

arXiv:2410.04955

arXiv

2410.04955

The topological characteristics of the $p$-wave Kitaev chains on a square lattice with nearest-neighbor and next-nearest-neighbor inter-chains hopping and pairing are investigated. Besides gapless exact zero-energy modes, this model exhibits topological gapless phase hosting edge modes, which do not reside strictly at zero energy. However, these modes can be distinguished from the bulk states. These states are known as pseudo- or quasi-Majorana Modes (qMMs). The exploration of this system's bulk spectrum and Berry curvature reveals singularities and flux-carrying vortices within its Brillouin zone. These vortices indicate the presence of four-fold Dirac points arising from two-fold degenerate bands. Examining the Hamiltonian under a cylindrical geometry uncovers the edge properties, demonstrating the existence of topological edge modes. These modes are a direct topological consequence of the Dirac semimetal characteristics of the system. The system is analyzed under open boundary conditions to distinguish the multiple MZMs and qMMs. This analysis includes a study of the normalized site-dependent local density of states, which pinpoints the presence of localized edge states. Additionally, numerical evidence confirms the robustness of the edge modes against disorder perturbations. The emergence of topological edge states and Dirac points with zero Chern number indicates that this model is a weak topological superconductor.

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