Multicopy Adaptive Local Discrimination: Strongest Possible Two-Qubit Nonlocal Bases

Ensembles of composite quantum states can exhibit nonlocal behaviour in the sense that their optimal discrimination may require global operations. Such an ensemble containing N pairwise orthogonal pure states, however, always be perfectly distinguished under adaptive local scheme if (N-1) copies state are available. In this letter, we provide examples orthonormal bases two-qubit Hilbert space whose 3 state. For system analyze multi-copy distinguishability ensembles full generality which turn assigns varying strength to different such ensembles. We also come up with separable less number than schemes. Our construction finds important application multipartite secret sharing tasks and indicates towards intriguing super-additivity phenomenon for locally accessible information.