### Nonclassicality Invariant of General Two-Mode Gaussian States.

*Ontology highlight*

**ABSTRACT**: We introduce a new quantity for describing nonclassicality of an arbitrary optical two-mode Gaussian state which remains invariant under any global photon-number preserving unitary transformation of the covariance matrix of the state. The invariant naturally splits into an entanglement monotone and local-nonclassicality quantifiers applied to the reduced states. This shows how entanglement can be converted into local squeezing and vice versa. Twin beams and their transformations at a beam splitter are analyzed as an example providing squeezed light. An extension of this approach to pure three-mode Gaussian states is given.

**SUBMITTER: **Arkhipov II

**PROVIDER: **S-EPMC4876421 | BioStudies | 2016-01-01

**SECONDARY ACCESSION(S): **10.1038/srep26523

**REPOSITORIES: ** biostudies

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