Characterizing Locally Indistinguishable Orthogonal Product States

Bennett [
Physical

Review

A
, vol. 59, no. 2, p. 1070, 1999] identified a set of orthogonal product states in the Hilbert space
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such that reliably distinguishing those states requires nonlocal quantum operations. While more examples have been found for this counterintuitive ldquononlocality without entanglementrdquo phenomenon, a complete and computationally verifiable characterization for all such sets of states remains unknown. In this paper, we give such a characterization for both
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and
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. As a consequence, we show that in both spaces, there is no additional set of a fundamentally different structure than those of the known instances.