Detectability Limits for Intra-Block Temporal Drift in Finite-Key Entanglement-Based QKD

• URL: http://arxiv.org/abs/2605.24230v1
• Date: Fri, 22 May 2026 21:18:46 GMT
• Title: Detectability Limits for Intra-Block Temporal Drift in Finite-Key Entanglement-Based QKD
• Abstract summary: We study the statistical detectability of intra-block temporal drift in finite-key entanglement-based quantum key distribution.<n>Dread is modeled as a mean-preserving Lipschitz perturbation of Bernoulli observables, capturing structured temporal variation.<n>The result quantifies a finite-block monitoring-resolution limit and is distinct from composable security certification.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We study the statistical detectability of intra-block temporal drift in finite-key entanglement-based quantum key distribution, with particular relevance to E91-type parameter estimation and monitoring. Drift is modeled as a mean-preserving Lipschitz perturbation of Bernoulli observables, capturing structured temporal variation that is invisible to global-average tests. For a block of size $n$ and confidence levels $(α,β)$, we formulate a minimax hypothesis-testing problem and define the minimal detectable amplitude. We derive matching lower and upper bounds yielding $δ_{\min}(n,α,β)=Θ(n^{-1/2})$: if $nδ^2 \to 0$, no level-$α$ procedure can guarantee nontrivial uniform power over the admissible drift class, whereas a calibrated CUSUM statistic detects drift at the matching scale. Explicit constants for linear, sinusoidal, and step profiles, together with simulations, confirm the predicted scaling collapse. The result quantifies a finite-block monitoring-resolution limit and is distinct from composable security certification.

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