Universal Entanglement Distillation
This study addresses the efficiency loss inherent in entanglement distillation of unknown bipartite quantum states. To overcome this limitation, the authors propose a universal adaptive protocol that integrates local operations and classical communication (LOCC) tomography, adaptive distillation, and a local robustness lemma. Theoretically, this work demonstrates that prior ignorance of the state incurs no asymptotic rate penalty, thereby establishing the optimal uniform distillation rate under worst-case scenarios. Furthermore, for fixed finite-dimensional systems, the proposed protocol achieves the optimal asymptotic distillation rate for arbitrary unknown states with vanishing error, attaining all achievable rates of distillable entanglement strictly below the theoretical limit. These results provide a rigorous foundation for efficient entanglement distillation without requiring prior knowledge of the underlying quantum states.