Increasing entanglement monotones by separable operations

Eric Chitambar, Wei Cui, Hoi Kwong Lo

Research output: Contribution to journalArticlepeer-review


Quantum entanglement is fundamentally related to the operational setting of local quantum operations and classical communication (LOCC). A more general class of operations known as separable operations (SEP) is often employed to approximate LOCC, but the exact difference between LOCC and SEP is unknown. In this letter, we compare the two classes in performing particular tripartite to bipartite entanglement conversions and report a gap as large as 12.5% between SEP and LOCC, which is the first known appreciable gap between the classes. Our results rely on constructing a computable entanglement monotone with a clear operational meaning that, unlike all other such monotones previously studied, is not monotonic under SEP. Finally, we prove the curious fact that convergent sequences of LOCC protocols need not be LOCC feasible in the limit.

Original languageEnglish (US)
Article number240504
JournalPhysical review letters
Issue number24
StatePublished - Jun 15 2012
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy


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