## Theoretical physics

Our theoretical physicists explore a range of current issues including:

- Theory of the optical equivalent of black holes (see below)
- Underpinning theory of the quantum optics used in quantum cryptography and quantum information theory
- Theory of strongly-interacting electrons in solids
- Field theory applied to the determine the limits of optical communication channels
- the theory of elementary particles using new algebras and string theories
- alternative formulations of quantum mechanics
- quantum concepts and quantum paradoxes
- relativistic quantum mechanics

Amongst Prof Ulf Leonhardt's studies in quantum optics is the prediction of the optical equivalent of black holes. His work predicts that such structures would have event horizons analogous to gravitational black holes, as indicated in the diagram alongside. With recent advances (elsewhere) in slowing down the speed of light to walking pace, there is now the real possibility of the practical realisation of his theoretical work.

Impression of black hole courtesy of Enrique Arilla.

Research in Ulf's team has also shown us how we might design "invisibility cloaks". We now know the optical prescription needed of materials to guide light around a region of space in such a way that there is no sign that the light has been deflected around the secret region.

And to add to invisibility cloaks, Ulf's team has now looked at the use of quantum mechanics to create quantum levitation. With the use of materials having a negative refractive index it may now be possible to use this material between small objects with the Casimir force then providing a repulsive force and the possibility of levitation. More obviously usefully, this might result in the reduction of friction effects in nano-machines.

Last updated BDS 8.07