We study a continuous variable (CV) dense-coding protocol, originally proposed to employ a two-mode squeezed state, using a general two-mode Gaussian state as a quantum channel. We particularly obtain conditions to manifest quantum advantage by beating two well-known single-mode schemes, namely, the squeezed-state scheme (best Gaussian scheme) and the number-state scheme (optimal scheme achieving the Holevo bound). We then extend our study to a multipartite Gaussian state and investigate the monogamy of operational entanglement measured by the communication capacity under the dense-coding protocol. We show that this operational entanglement represents a strict monogamy relation, by means of Heisenberg's uncertainty principle among different parties, i.e., the quantum advantage for communication can be possible for only one pair of two-mode systems among many parties.
@article{arxiv.1408.1153,
title = {Continuous-variable dense coding via a general Gaussian state: Monogamy relation},
author = {Jaehak Lee and Se-Wan Ji and Jiyong Park and Hyunchul Nha},
journal= {arXiv preprint arXiv:1408.1153},
year = {2014}
}