Gaussian Entanglement for Quantum Key Distribution from a Single-Mode Squeezing Source

We report the realization of an Einstein-Podolsky-Rosen (EPR) entanglement source for gaussian continuous-variable quantum key distribution at 1550 nm. Our source is based on a single continuous-wave squeezed vacuum mode with 11.1 \pm 0.1 dB squeezing, combined with vacuum at a balanced beam splitter. The conditional variance product (Reid criterion, Phys. Rev. A 40 913, 1989) of this source is 0.31 \pm 0.01, well below the classical threshold 1. The maximal achievable key rate with security against collective attacks is of 0.38 bits/measurement. Although only a single squeezed beam was used, the conditional variance product is comparable to the best reported values using two squeezed beams