arXiv subjects

Yi-Fan Yang

Publications and source records attributed to Yi-Fan Yang.

5 recordsLinked to original sources

arXiv2026

Intriguing Electronic Structures of C8 and C12 Carbon Rings

We report on the ground and numerous excited electronic states. In the ground state the C4n rings are closed-shell systems possessing polyynic structures and can be classified as double anti-aromatic molecules. In their energetically lowest lying triplet state the rings exhibit aromatic cumulenic structures. The overall change in the electronic structures is rather dramatic upon the found moderate geometric changes from polyynic to cumulenic structure. Among others, Hund's rule is violated in both C8 and C12 in their cumulenic structures. We mention that until now, graphene is the only carbon allotrope reported to violate Hund's rule. The reasons for the violation are analyzed. Much effort has been invested to understand the relaxation pathways of the low-lying states leading the C8 from polyynic to cumulenic geometry and vice versa. On its minimum energy path, the first singlet excited state changes from open-shell character in the polyynic structure to a closed-shell state in the cumulenic structure. The cumulenic state lowest in energy is an open-shell singlet which relaxes to the closed-shell polyynic ground state.

physics.chem-ph↗

arXiv2026

Charging Dynamics in a Distance-Modulated Planar Quantum-Battery Architecture

While the spatial arrangement of individual units is essential for the physical implementation of quantum batteries, geometry-dependent interactions are rarely explicitly incorporated into existing theoretical models. To address this, we propose a planar many-body quantum-battery architecture consisting of coupled resonators. By introducing a distance-dependent function to modulate both the inter-battery coupling and tunneling, we investigate the open-system charging dynamics in the strong-coupling regime using a Redfield master-equation approach. Using ergotropy as the primary figure of merit, we demonstrate that the charging performance is highly sensitive to the inter-battery distance, nearest-neighbor coupling strength, and environmental conditions. Specifically, decreasing the inter-battery distance within an optimal window suppresses charging fluctuations and accelerates the system's approach to a steady charged state. However, an excessively short distance amplifies environmental dissipation, thereby degrading the overall performance. Furthermore, while overly strong inter-battery coupling induces post-charging instability, moderate coupling achieves a favorable balance between maximum stored energy and stability. We also establish that the system-bath coupling and bath cutoff frequency predominantly govern the charging timescale, and that the planar architecture maintains its robustness against thermal fluctuations over a broad temperature range. These results highlight the critical role of geometry-controlled interactions in many-body quantum batteries, providing a theoretical foundation for the design and optimization of two-dimensional quantum energy-storage devices.

quant-ph↗

arXiv2025

Multi-timescale time encoding for CNN prediction of Fenna-Matthews-Olson energy-transfer dynamics

Machine learning simulations of open quantum dynamics often rely on recursive predictors that accumulate error. We develop a non-recursive convolutional neural networks (CNNs) that maps system parameters and a redundant time encoding directly to excitation-energy-transfer populations in the Fenna-Matthews-Olson complex. The encoding-modified logistic plus $\tanh$ functions-normalizes time and resolves fast, transitional, and quasi-steady regimes, while physics-informed labels enforce population conservation and inter-site consistency. Trained only on $0\sim 7 ps$ reference trajectories generated with a Lindblad model in QuTiP, the network accurately predicts $0\sim100 ps$ dynamics across a range of reorganization energies, bath rates, and temperatures. Beyond $20 ps$, the absolute relative error remains below 0.05, demonstrating stable long-time extrapolation. By avoiding step-by-step recursion, the method suppresses error accumulation and generalizes across timescales. These results show that redundant time encoding enables data-efficient inference of long-time quantum dissipative dynamics in realistic pigment-protein complexes, and may aid the data-driven design of light-harvesting materials.

physics.chem-ph↗

arXiv2025

Rapid and Stable Collective Charging and Discharge Suppression in Strongly Coupled Many-Body Quantum Batteries

Achieving rapid and stable energy storage in quantum batteries (QBs) remains a key challenge, particularly under strong system-environment coupling where non-Markovian effects become prominent. While most previous studies focus on weak coupling regimes, we propose a many-body QB model exhibiting collective charging and discharge suppression in a non-perturbative regime. The model adopts a $\Lambda$-type configuration where multiple battery units share a common excited state and have individual ground states, forming an effective collective structure. To accurately capture the dynamics under strong coupling, the system's time evolution is governed by a Redfield-type master equation tincorporating memory effects via a Debye spectral density. We quantify the stored energy using ergotropy and analyze the impact of tunneling, driving strength, spectral width, and environmental temperature on charging performance. Numerical simulations reveal that optimized driving and reservoir engineering can simultaneously achieve rapid and stable charging while suppressing energy leakage. These results provide theoretical insight into strong-coupling thermodynamics and guide the design of robust QB platforms using solid-state or atomic systems.

quant-ph↗

arXiv2020

Mediated Asymmetric Semi-Quantum Key Distribution

This study proposes a new mediated asymmetric semi-quantum key distribution (MASQKD) protocol. With the help of a dishonest third party, two classical participants, who have only limited asymmetric quantum capabilities, can share a secret key with each other. The proposed protocol is shown to be immune to several well-known attacks. Furthermore, an improved MASQKD protocol is proposed in which the quantum capabilities of one participant can be further reduced.

quant-ph↗