Quantum information and reality

Andreas Doering ( Oxford University Computing Laboratory )

Quantum Information Theory (QIT) is in large parts a practical endeavour that utilises some of the counterintuitive features of quantum systems to perform computational tasks faster than classical systems can. But since some of the still mysterious aspects of quantum theory are used, one is inevitably lead into questions on the foundations of quantum theory, too. For example, there is no direct access to quantum information: all one can do to extract information from a quantum system is to perform a measurement on a qubit, the alleged carrier of quantum information, to obtain a classical bit. This points to the deeper problem that the usual mathematical formalism of quantum theory does not provide a picture of reality, but needs an interpretation in terms of measurements, classical observers etc. After briefly reviewing some aspects of QIT from a conceptual perspective, I will sketch a new mathematical formulation of quantum theory that allows for a realist interpretation -- the topos approach.