**Quantum Information, so what is it?**

Quantum information theory hovers in an odd way between mathematics and physics, and constitutes a general framework for thinking about quantum systems. It is based around the slippery notion of "information", and provides a powerful language in which to describe the abstract properties of quantum states that are independent of their particular physical realisations. Because of this it has a broad scope and finds application in very different areas of quantum physics.

Often an area of physics is associated with a range of length-scales or energies, however in contrast quantum information theory is associated with regimes of "non-classicality". Such regimes can occur at any length-scales and any energies. Within these non-classical regimes, quantum systems no longer possess properties in the familiar sense. This fact lies at the heart of what is so strange about quantum theory, and teasing out its implications is a surprisingly subtle and deep problem.

Often an area of physics is associated with a range of length-scales or energies, however in contrast quantum information theory is associated with regimes of "non-classicality". Such regimes can occur at any length-scales and any energies. Within these non-classical regimes, quantum systems no longer possess properties in the familiar sense. This fact lies at the heart of what is so strange about quantum theory, and teasing out its implications is a surprisingly subtle and deep problem.