Quantum Information Processing with Continuous Variables and Atomic Ensembles

摘要: This thesis presents three different results in quantum information theory. The first result addresses the theoretical foundations of metrology. Heisenberg limit considered as ultimate metrology sets a lower bound on how precisely physical quantity can be measured given certain amount resources any possible measurement. Recently, however, several measurement procedures have been proposed which seemed to surpassed. led an extensive debate over question sensitivity scales with and computational that are used estimation procedures. Here, we reconcile definition relevant information-theoretical scaling terms query complexity network. leads novel applies all conceivable second reveals close relationship between Deutsch-Jozsa algorithm continuous-variable systems. develop general procedure, characterized by two parameters, unifies parameter algorithm. procedure estimates value unknown Heisenberg-limited precision or solves problem single run without use entanglement. third illustrates principles govern interaction light matter efficiently employed create resource for (one-way) computer. More specifically, demonstrate theoretically scheme based atomic ensembles dipole blockade mechanism generation so-called cluster states step. is significantly more efficient than known robust probabilistic entangling operation.