Exploring Hilbert Space: accurate characterisation of quantum information

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.

4 pages, 3 figures. Submitted to Physical Review A

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• Experimental quantum teleportation
• On the Measurement of Qubits
• Maximizing the entanglement of two mixed qubits
• Entanglement Manipulation and Concentration

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