Continuous-variable entanglement on a chip

Encoding quantum information in continuous variables, as the quadrature of electromagnetic fields, is a powerful approach to quantum information science and technology. Continuous-variable entanglement (light beams in Einstein-Podolsky-Rosen, or EPR, states) is a key resource for quantum information protocols and enables hybridization between continuous-variable and single-photon discrete-variable qubit systems. However, continuous-variable systems are currently limited by their implementation in free-space optical networks, and the demand for increased complexity, low loss, high-precision alignment and stability, as well as hybridization, require an alternative approach. Here we present an integrated photonic implementation of the key capabilities for continuous-variable quantum technologies - the generation and characterization of EPR beams in a photonic chip. When combined with integrated squeezing and non-Gaussian operations, these results will open the way to universal quantum information processing with light.