2025/09/29 by Zahidur Rezwan Ratul, Ratul, Zahidur Rezwan
Computer Science · #68Q12 #81P94 #94A60 #Chaos-based Image/Signal Encryption #E.3 #F.1.2 #FOS: Physical sciences #K.6.5 #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Physics (quant-ph)
paper · pdf · doi:10.48550/arxiv.2509.25078
openalex publication_date 2025/09/29 · openalex created_date 2025/10/09 · openalex updated_date 2026/07/28
We study Semi-Quantum Key Distribution (SQKD) with a focus on finite-size security bounds, developed through three complementary perspectives. (i) Spectral disturbance: wrong-basis Lüders updates produce closed-form spectra and purity loss, which serve as basis-independent indicators of disturbance. (ii) Operator-theoretic reduction: in Z/Z-sifted rounds, intercept-resend attacks can be represented as an effective depolarizing channel, characterized by a fidelity-QBER relation. (iii) Entropic trade-offs: Maassen-Uffink and memory-assisted uncertainty relations certify security through X tests and reflection rounds, even when the sifted QBER is low. The exposition provides step-by-step derivations supported by physically interpretable figures, and the framework concludes with finite-size estimates based on concentration inequalities that are suited for practical parameter estimation.