# Capability of local operations and classical communication for distinguishing bipartite unitary operations. (arXiv:1711.03865v1 [quant-ph])

The problem behind this paper is, if the number of queries to unitary

operations is fixed, say $k$, then when do local operations and classical

communication (LOCC) suffice for optimally distinguishing bipartite unitary

operations? We consider the above problem for two-qubit unitary operations in

the case of $k=1$, showing that for two two-qubit entangling unitary operations

without local parties, LOCC achieves the same distinguishability as the global

operations. Specifically, we obtain: (i) if such two unitary operations are

perfectly distinguishable by global operations, then they are perfectly

distinguishable by LOCC too, and (ii) if they are not perfectly distinguishable

by global operations, then LOCC can achieve the same optimal discrimination

probability as the global operations.