Quantum mutual information of an entangled state propagating through slow- and fast-light media

Abstract

Due to its vital role in many quantum information and communication protocols, much theoretical and experimental work has been conducted in order to investigate the fundamental properties of entanglement. In this work we describe an experimental investigation into the behavior of continuous-variable entanglement and quantum mutual information upon propagation through slow-and fast-light media. A four-wave mixing process in warm atomic vapor is used to generate an entangled two-mode squeezed vacuum state of light. One of the two modes of the resulting state is then sent through a second four-wave mixing process that is tuned to exhibit either slowor fast-light properties. The cross-correlation and quantum mutual information shared between the resulting modes is quantified, and differences in their behavior after propagation through slow-and fast-light media are discussed.