title: Stimulated emission of polarization-entangled photons.
abstract: Entangled photon pairs-discrete light quanta that exhibit non-classical correlations-play a crucial role in quantum information science (for example, in demonstrations of quantum non-locality, quantum teleportation and quantum cryptography). At the macroscopic optical-field level non-classical correlations can also be important, as in the case of squeezed light, entangled light beams and teleportation of continuous quantum variables. Here we use stimulated parametric down-conversion to study entangled states of light that bridge the gap between discrete and macroscopic optical quantum correlations. We demonstrate experimentally the onset of laser-like action for entangled photons, through the creation and amplification of the spin-1/2 and spin-1 singlet states consisting of two and four photons, respectively. This entanglement structure holds great promise in quantum information science where there is a strong demand for entangled states of increasing complexity.
authors.affiliation: Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, UK. a.lamas@qubit.org
authors.forename: A
authors.initials: A
authors.lastname: Lamas-Linares
authors.forename: J C
authors.initials: JC
authors.lastname: Howell
authors.forename: D
authors.initials: D
authors.lastname: Bouwmeester