arXiv subjects

Hao-Wen Liu

Publications and source records attributed to Hao-Wen Liu.

4 recordsLinked to original sources

arXiv2026

Experimentally validated quantum-secure federated learning over a multi-user quantum network

Federated learning enables decentralized, privacy-preserving training but remains vulnerable to privacy leakage in the quantum era. Quantum federated learning (QFL) offers a promising path towards enhanced security and efficiency. However, a practical and experimentally validated QFL protocol utilizing near-term quantum techniques to address data privacy has been lacking. Here we present QuNetQFL, a QFL protocol implemented on quantum networks, in which local model updates are masked with distributed quantum secret keys, offering information-theoretic security during aggregation. We experimentally validate the protocol on a four-client quantum network and benchmark its performance using the generated keys on quantum and real-world datasets. Adding a single quantum client significantly improves global accuracy for classifying multipartite entangled and non-stabilizer quantum datasets. For language tasks, we apply QuNetQFL to sentiment analysis by federated fine-tuning of a hybrid classical-quantum language model, achieving comparable and robust performance in simulation and on real quantum hardware. Large-scale simulations further demonstrate scalability to 200 clients for handwritten-digit recognition, with rapid convergence and a $75\%$ reduction in communication cost via model compression. Our work establishes a practical and scalable route to quantum-secure federated learning for the emerging quantum internet.

quant-ph↗

arXiv2021

Photoinduced charge density wave transition like a puppet on a string

Charge density wave (CDW) materials can undergo an ultrafast phase transition after an ultrashort laser pulse excitation, and the suggested underlying mechanisms have always been associated with two main features: excitonic interaction-induced CDW charge order and electron-phonon coupling-induced periodic lattice distortion (PLD). Here, beyond these two mechanisms, we reveal that photoexcitation induced CDW phase transition in the prototypic CDW example 1T-TiSe2 is similar to a puppet on a string: six Ti-Se bonds connected to each distorted Ti atom acting as six strings controlling the PLD and in turn the CDW orders. The photoexcitation induced modulation on charge population of the Ti-Se bonds generates a laser-fluence-dependent interatomic-repulsive force along each Ti-Se bond. The nonequal length of these six Ti-Se bonds gives rise to a net force exerted on the central distorted Ti atom to push it toward the suppressing of the PLD and thus the CDW orders. We further illustrate that the dynamics of each distorted Ti atom behaves as though it attached to a spring in a simple harmonic motion with a fluence-dependent oscillation frequency, uniting two previously reported scaling laws for phase transition time. These findings significantly advance the understanding of CDW instability and provide new insights into how photoexcitation induced modulation on charge population may lead to phase transitions by directly connecting interatomic forces with reaction pathways.

cond-mat.mtrl-sci↗

arXiv2021

Uniting the order and disorder dynamics in photoexcited VO2

Photoinduced phase transition (PIPT) is always treated as a coherent process, but ultrafast disordering in PIPT is observed in recent experiments. Utilizing the real-time time-dependent density functional theory (rt-TDDFT) method, here, we track the motion of individual vanadium (V) ions during PIPT in VO2 and uncover that their coherent or disordered dynamics can be manipulated by tuning the laser fluence. We find that the photoexcited holes generate a force on each V-V dimer to drive their collective coherent motion, in competing with the thermal-induced vibrations. If the laser fluence is so weak that the photoexcited hole density is too low to drive the phase transition alone, the PIPT is a disordered process due to the interference of thermal phonons. We also reveal that the photoexcited holes populated by the V-V dimerized bonding states will become saturated if the laser fluence is too strong, limiting the timescale of photoinduced phase transition.

cond-mat.mtrl-sci↗

arXiv2021

Physical Layer Security for NOMA-Enabled Multi-Access Edge Computing Wireless Networks

Multi-access edge computing (MEC) has been regarded as a promising technique for enhancing computation capabilities for wireless networks. In this paper, we study physical layer security in an MEC system where multiple users offload partial of their computation tasks to a base station simultaneously based on non-orthogonal multiple access (NOMA), in the presence of a malicious eavesdropper. Secrecy outage probability is adopted to measure the security performance of the computation offloading against eavesdropping attacks. We aim to minimize the sum energy consumption of all the users, subject to constraints in terms of the secrecy offloading rate, the secrecy outage probability, and the decoding order of NOMA. Although the original optimization problem is non-convex and challenging to solve, we put forward an efficient algorithm based on sequential convex approximation and penalty dual decomposition. Numerical results are eventually provided to validate the convergence of the proposed algorithm and its superior energy efficiency with secrecy requirements.

cs.IT↗