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Exploring Hilbert Space: accurate characterisation of quantum information

A. G. White·D. F. V. James·W. J. Munro·P. G. Kwiat
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Abstract

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 downconversion. 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.

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A. G. White, D. F. V. James, W. J. Munro, P. G. Kwiat. 2001-08-20. Exploring Hilbert Space: accurate characterisation of quantum information. https://doi.org/10.1103/physreva.65.012301

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