Based on the Fourth International Conference on Quantum Communication, Measurement and Computing, this volume brings together scientists working in the interdisciplinary fields of quantum communication science and technology. In contrast to the previous conferences in this series, which were mainly theoretical, QCH '98 devoted more attention to the experimental aspects. Topics include quantum information theory, quantum computing, quantum communication systems, cryptography, new quantum effects and their experiments, generation and detection of nonclassical light, quantum noise, shastic processes and filtering, and quantum measurement theory.