Experimental single-query discrimination of entangling unitaries using local operations and classical communication on a programmable silicon photonic chip
Phys. Rev. A 113, 022619 – Published 20 February, 2026
DOI: https://doi.org/10.1103/vxgt-7f2y
Abstract
Quantum information processing relies on unitary operations to control quantum evolution, whose distinguishability reveals the fundamental differences between quantum processes. In principle, global strategies can realize optimal discrimination, but they remain impractical in distributed systems limited to local operations and classical communication (LOCC). Li et al. [Phys. Rev. A 96, 052327 (2017)] pointed out that an LOCC strategy can achieve the same optimal distinguishability as global strategies with a single query. In this study, we experimentally demonstrate LOCC-based discrimination of two-qubit entangling unitary operations on a programmable silicon photonic chip in the single-query setting, covering three representative cases: perfect, minimum-error, and unambiguous discrimination. Our results demonstrate that the LOCC strategy alone is sufficient to optimally discriminate any pair of two-qubit unitary operations, yielding a discrimination capability comparable to that of global strategies. For the nonperfectly distinguishable cases, error-free discrimination was realized through positive operator-valued measure (POVM) measurements, albeit with reduced efficiency. The experimentally demonstrated method for discriminating entangling unitary operations offers potential applications in quantum authentication and distributed quantum computing.
