Research – University of Copenhagen

Theoretical research at the group

Today, experiments have advanced to a stage where one can have complete control of individual quantum systems, such as single atoms or photons. We are making theories for how to exploit this extreme experimental control to gain new insight into nature and to construct quantum computers and other applications.

Quantum information

One of the main research areas of the group is the physical realization of quantum information processing. By constructing quantum computers where information is stored in for instance individual atoms, it is possible to exploit the laws of quantum mechanics to process information more efficiently. Furthermore by sending information in the form of single photons, one can encode information such that it is impossible for an eavesdropper to read the information being sent. Realizing the potential of these ideas, however, requires that one can actually build the devices, and we are developing theories for how to do this in practice.

Sketch of a scheme for dissipative generation of entanglement in optical cavities.

A particular focus area is quantum repeaters and light-matter quantum interfaces. To transmit quantum information over long distances it is important to have quantum repeater stations along the way to counteract the losses in the optical fibers used to transmit the photons. An essential ingredient in such a quantum repeater is a light-matter quantum interface enabling the exchange of information between light and matter. We are developing theories for how to make such interfaces in a number of systems ranging from individual or ensembles of atoms to solid state systems. Furthermore we develop theories for how to connect the interfaces into quantum repeaters.

Ultra cold atoms

Understanding the properties of strongly correlated many particle quantum systems is a major challenge. Even the most simple models for interacting quantum systems quickly becomes impossible to solve as the number of particle increases. To understand the simple models an alternative approach is to build quantum simulators which mimics the dynamics of a certain model. This is particularly interesting for ultra cold atoms, where the parameters can be controlled almost at will. Thereby one can use atoms to realize some of the quintessential models of condensed matter physics and learn about their properties. We are making theories for how to realize this with the experimental techniques presently available.

Outline of method for probing antiferromagnetic ordering in optical lattices.