The theoretical quantum optics group is headed by Prof. Anders Søndberg Sørensen and was established at the Niels Bohr Institute in 2004.

In 2006-2013 the group was part of the Danish Quantum optics center (Quantop) funded by DNRF and in 2012-2017 the group received funding through a consolidator grant from the ERC for research on Quantum Information and Open System (QIOS 2012-2017). Currently, the group is part of the Center for Hybrid Quantum Network (Hy-Q) funded by DNRF and a member of the Quantum Internet Alliance.

The research of the group covers a broad range of topics in theoretical quantum optics. Special focus is on methods to realize quantum information processing in practice and we study this in various systems, ranging from atoms and photons to solid state devices. In addition we also make theories for ultra cold atoms. 

The group has a strong collaboration with the quantum optics laboratory, the quantum photonics group and the Schliesser lab at the Niels Bohr Institute. We also have a long lasting collaboration with the Lukin group at Harvard University.

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.

View publications here >>

We are always looking for motivated and dedicated students with an interest in what we do. Please contact Prof. Anders S. Sørensen at anders.sorensen*nbi.dk if you are interested.