arXiv subjects

Chenlei Fang

Publications and source records attributed to Chenlei Fang.

3 recordsLinked to original sources

arXiv2026

EMAN: Optimization-Driven Capacity Growth through Path Emergence in Multi-Task Learning

Existing multi-task learning methods rely on hard sharing, multiple paths or experts, adaptive sharing, and dynamic expansion. However, their capacity changes are usually constrained by predefined structures or triggered by task boundaries and conflict signals. This raises a fundamental question: can a network start from exact single-path computation and grow a new independent path only when persistent optimization evidence appears? We propose the Emergent Modular Atomic Network (EMAN), an optimization-driven framework for exposing an antisymmetric growth direction through latent relative phases without instantiating a second path, and for monitoring multiple decision signals during training to transform local optimization evidence into a structural decision. EMAN materializes two equal-capacity independent paths only after certification. EMAN adaptively allocates shared and task-specific representation capacity to accommodate varying task requirements. Extensive experiments on controlled rank settings, PASCAL-Context, and NYUv2 validate its effectiveness, achieving improved performance at a competitive computational cost.

cs.LG↗

arXiv2025

Practical security of local local oscillator continuous-variable quantum key distribution systems with pulse width mismatch

In continuous-variable quantum key distribution (CVQKD) systems, using a local local oscillator (LLO) scheme removes the local oscillator side channel, enhances Bob's detection performance and reduces the excess noise caused by photon leakage, thereby effectively improves the system's security and performance. However, in this scheme, since the signal and the LO are generated by different lasers and the signal propagates through the untrusted quantum channel, their pulse widths may become mismatched. Such mismatches may reduce the precision of detection at Bob, affecting parameter estimation processes and leading to inaccurate calculations of the secret key rate. Moreover, mismatches may introduce potential security loopholes. Thus, this paper investigates the practical security issues of the LLO-CVQKD system when pulse width mismatch occurs between the local oscillator and the signal. We first model the case of pulse width mismatch and analyze its impact on Bob's detection. Then, we simulate the secret key rate under different mismatch levels. Based on the analysis, we find that under such mismatch, the key parameters involved in secret key rate calculation are incorrectly estimated, leading to an overestimation of the system's secret key rate. Therefore, this imperfect mismatch can open a loophole for Eve to perform attacks in practical systems. To close this loophole, we design a scheme at Bob to monitor the pulse widths of both the signal and the local oscillator, and to reshape the waveform of the local oscillator so that the two lights are matched again. This method eliminates the adverse effects caused by pulse width mismatch and effectively resists Eve's attacks which exploit this loophole.

quant-ph↗

arXiv2024

Quantum hacking: Induced-photorefraction attack on a practical continuous-variable quantum key distribution system

We explore a new security loophole in a practical continuous-variable quantum key distribution (CVQKD) system, which is opened by the photorefractive effect of lithium niobate-based (LN-based) modulators. By exploiting this loophole, we propose a quantum hacking strategy, i.e., the induced-photorefraction attack, which utilizes the induced photorefraction on the LN-based modulators to hide the classical intercept-resend attack. Specifically, we show that the induced photorefraction can bias the response curve of the LN-based modulator, which will affect the intensity of the modulated signal. Based on the investigation of the channel parameter estimation under above influence, we further analyze the secret key rate of the practical CVQKD system. The simulation results indicate that the communication parties will overestimate the secret key rate, which reveals that Eve can actively open the above loophole by launching the induced-photorefraction attack to successfully obtain the secret key information. To defend against this attack, we can use a random monitoring scheme for modulation variance to determine this attack, and use an improving optical power limiter to effectively mitigate the irradiation beam. Apart from these countermeasures, we also propose using the Sagnac-based IM to stabilize the practical CVQKD system, which can minimize the above effects.

quant-ph↗