Prof. Dr. Michael Köhl

Raum 5.020
Wegelerstrasse 8
53115 Bonn 
Tel.: +49-228-73 4899
Fax: +49-228-73 4038


Tina Naggert

Raum 5.017
Wegelerstrasse 8
53115 Bonn 
Tel.: +49-228-73 4898
Fax: +49-228-73 4038

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Open Positions

PhD & postdoc project in ultracold Fermi gases

We have an open PhD position on ultracold Fermi gases. The topic of ultracold Fermi gases currently is very "hot" because it holds the promise to achieve quantum simulation of complex quantum systems that cannot be modeled otherwise.  In recent years, it has become possible to assemble strongly correlated quantum many-body systems in a bottom-up approach using ultracold atomic quantum gases. This novel approach has created the purest and most widely tunable “materials” in which quantum many-body physics can be studied. They are considered ideal candidates for both unravelling the mysteries of observed, but not yet understood effects in the solid state and for realizing completely new quantum phases, very much in the sense of Feynman’s concept of a “quantum simulator”. Perhaps most importantly, cold atomic gases provide an ideal testing ground for non-equilibrium evolution because the tuneability is very rapid compared to the typical energy/time scales of the system and the dynamics remains coherent for long times by virtue of their weak coupling to the environment.

In this PhD project we plan to explore two-dimensional Fermi gases with a specific focus on high-resolution imaging and local manipulation of the gas. In-situ imaging of a two-dimensional Fermi gas in an optical lattice will reveal its low-temperature quantum phases such as the Mott insulator or the antiferromagnet. Of particular interest for the PhD project will be the dynamics of these phases, i.e. how they form and how they respond to perturbations and to dissipative coupling, e.g. by near-resonant light. Usually, dissipation is linked to heating and decoherence, however, recently it has been theoretically predicted that suitably tailored dissipation could -- quite counterintuitively --  actually stabilize complex (and yet unobserved) quantum phases. 

You should have a strong interest in performing experiments at the forefront of quantum physics. Background knowledge in relevant topics (quantum gases, optical lattices, quantum metrology, laser cooling, ...) and technology (optics, lasers, UHV systems, electronics, data acquisition) is benficial. We will provide a stimulating environment to perform research on the cutting edge of both science and technology. The research efforts take place in a small team with PhD students and postdocs.

For further scientific information, please contact .


PhD & postdoc: Trapped ions in high-finesse optical cavities: Building the quantum internet

Small numbers of qubits can be well controlled in variety of systems, however, increasing the size of quantum computers to larger systems is very difficult. A remedy to this problem is using a distributed system, a quantum network. Quantum networks consist of local nodes, where qubit states are manipulated and stored, interconnected by transmission lines for the controlled distribution of entanglement. The latter is preferably achieved using photons to losslessly bridge large distances. So far, the arguably most advanced realizations of local quantum computers, trapped atomic ions (see Physics Nobel prize 2012), were precluded from efficient quantum networking because they could only be coupled weakly to single photon modes. Recently, we have demonstrated a new technique to overcome this limitation by coupling a single trapped ion to a miniature optical resonator formed by tips of optical fibers [M. Steiner et al., Phys. Rev. Lett., in press (2013)].

In the PhD project, this new technique should be developed into a fiber-based quantum network in which several ions will be interconnected by single-photon light fields. The experiments will explore the new regime of quantum information processing with decentralized processing units, which has interesting technological implications and addresses fundamental questions regarding the distribution of quantum information in such networks. Moreover, the planned experiments will also open possibilities to study the dynamics of strongly correlated photons in arrays of optical cavities, which is intimately linked to the physics of the Bose-Hubbard model.

We are looking for an excellent candidate with a strong background in experimental physics and a passion for setting up and conducting challenging experiments. The research work offers training in both cutting edge technology (quantum optics, fiber optics, photonics) and fundamental concepts of modern quantum physics.

For further information, please contact .

Open PhD/postdoc announcement

If you are interested in joining one of our projects which is not specifically listed here, please contact .

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