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quant-ph2026

Quantum Constrained Hamiltonian Descent

Yoshihiko Abe, Ryo Nagai

We propose Quantum Constrained Hamiltonian Descent (QCHD), a continuous-time quantum framework for optimization under smooth equality constraints. The unconstrained counterpart, Qu…

quant-ph2026

Thermalization in a repeated-interaction model with memory effects

Kanji Nishii, Ryo Nagai, Yoshihiko Abe

We study how memory affects the thermalization of a qubit in a repeated-interaction model. In our model, a memory qubit interacts repeatedly with the system, while both qubits unde…

quant-ph2026

Surface-Code Thresholds and Qubit Footprints in Shuttling-Based Spin-Qubit Railways

Arun John Moncy, Reza Dastbasteh, Josu Etxezarreta Martinez +5

We present a fault-tolerant mapping of rotated surface codes onto a silicon spin-qubit railway architecture, utilizing electron shuttling to resolve the wiring fan-out…

quant-ph2026

Quantum Riemannian Hamiltonian Descent

Yoshihiko Abe, Ryo Nagai

We propose Quantum Riemannian Hamiltonian Descent (QRHD), a quantum algorithm for continuous optimization on Riemannian manifolds that extends Quantum Hamiltonian Descent (QHD) by…

quant-ph2025

Digital-Controlled Method of Conveyor-Belt Spin Shuttling in Silicon for Large-Scale Quantum Computation

Ryo Nagai, Takashi Takemoto, Yusuke Wachi +1

We propose a digital-controlled conveyor-belt shuttling method for silicon-based quantum processors, addressing the scalability challenges of conventional analog sinusoidal impleme…