| Efficient sources of entangled particles are essential for the experimental realization of many novel features of quantum information processing. In addition to serving as tools to verify certain fundamental notions about the nature of light and matter, entangled photon sources are a prerequisite for such applications as quantum teleportation of a photon polarization state.; To date, the most useful method for producing entangled photons has been parametric downconversion in χ(2) crystals. Tremendous advances in the field have been made using such sources, but fiber-based sources, which rely on the χ(3) nonlinearity in glass, provide some advantages and new flexibility. For example, the ability to generate entangled particles and distribute them to far away locations is highly desirable. A fiber-based source integrates naturally with the existing low-loss fiber-optic communication infrastructure, and therefore is highly advantageous when distribution of entanglement over optical fibers is desired.; In order to fully exploit the χ(3) nonlinearity in glass one must first fully understand it. The coupled-wave theory of four-wave mixing is reproduced here where special attention has been given to experimental realization of the effect using the available optical fibers. Numerical modelling tools have been developed and two sets of experiments have been performed; one using microstructure fibers, and the other using standard dispersion-shifted fiber. This theory, modelling, and experimentation thoroughly explores the classical aspects of four-wave mixing and reveals that nonlinear interactions can be phase matched and parametric gain can be achieved.; Four-wave mixing is really a four-photon process during which two photons are destroyed and two new photons are emitted. Of particular interest is the fact that the pairs of photons emitted during the four-wave mixing process are quantum-mechanically correlated, and thus can be used to generate various forms of entanglement. Experiments with both dispersion-shifted and microstructure fibers reveal these quantum-mechanical correlations. By time multiplexing two orthogonally polarized four-wave mixing processes one can obtain polarization-entangled photons and demonstrate a violation of a form of Bell's inequalities. |
