Item

Abstract

Continuous variable entanglement is a fundamental resource for many quantum
information tasks. Important protocols like superactivation of zero-capacity
channels and finite-size quantum cryptography that provides security against
most general attacks, require about 10 dB two-mode squeezing. Additionally,
stable phase control mechanisms are necessary but are difficult to achieve
because the total amount of optical loss to the entangled beams needs to be
small. Here, we experimentally demonstrate a control scheme for two-mode
squeezed vacuum states at the telecommunication wavelength of 1550 nm. Our
states exhibited an Einstein-Podolsky-Rosen covariance product of 0.0309 \pm
0.0002, where 1 is the critical value, and a Duan inseparability value of 0.360
\pm 0.001, where 4 is the critical value. The latter corresponds to 10.45 \pm
0.01 dB which reflects the average non-classical noise suppression of the two
squeezed vacuum states used to generate the entanglement. With the results of
this work demanding quantum information protocols will become feasible.