Exploring Hilbert Space : accurate characterisation of quantum information

[摘要] We report the creation of a wide range of quantum states with controllable degrees of entanglement and entropy using an optical two-qubit source based on spontaneous parametric down conversion. The states are characterised using measures of entanglement and entropy determined from tomographically determined density matrices. The Tangle-Entropy plane is introduced as a graphical representation of these states, and the theoretic upper bound for the maximum amount of entanglement possible for a given entropy is presented. Such a combination of general quantum state creation and accurate characterisation is an essential prerequisite for quantum device development. Notes: A. G. White, Department of Physics, University of Queensland, Brisbane, Queensland 4072 Australia. D.F.V. James, Theory Division, T-4; Physics Division, P-23; Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. P.G. Kwiat, Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801, USA 4 Pages

[发布机构] HP Development Company

[学科分类] 计算机科学（综合）

[关键词] controllable state production;tomographic reconstruction;experimental determination of entanglement