Research projects

	Single atom quantum interfaces One of the cleanest quantum information storage systems are internal degrees of freedom of single atoms. We want to understand the basics of atom-light interaction for future quantum interfaces.
	Thermal Light and Applications Photon bunching properties of thermal light, combined with modern detection and preparation techniques, allow for applications ranging from lidar to observations in astronomy.
	Entanglement tests with photon pairs Bell inequalities are a powerful tool in discriminating whether nature is better described by classical or non-local theories. We explore how close an experiment can approach the prediction of quantum physics, and explore an algorithmic alternative of assessing non-locality.
	Four-wave mixing Efficent transfer of entanglement in photons to stationary qubits such as atoms requires narrowband photons. We generate narrowband correlated photon pairs via four wave mixing in a Rubidium-87 MOT.
	Quantum Random Numbers We use quantum noise in a photodetection process for a fast compact physical random number generator.
	Sources of entangled photon pairs Most quantum information experiments depend on strong sources for entangled photons. We try to improve the entanglement quality, brightness and usability of such sources based on parametric down conversion.
	Quantum cryptography A practical application of quantum information ideas to establish a secure communication channel. Our experiments implement entanglemend-based cryptography protocols via a free-space optical link.

Past projects

	Magnetometry with diamond NV centers Single NV centers in diamond are photostable single quantum systems that can be used for a number of quantum information processing tasks. Here we use the Larmor precession in the electronic ground states of an NV center as a highly sensitive microscopic magnetic field probe.
	Quantum hacking Quantum key distribution can be really secure if you have a clean system and you know everything about it. Realistic systems, however, do have issues, and we look into physical vulnerabilities of representative implementations.
	Multiphoton entanglement Complex quantum information protocols can be based on multiphoton entanglement. We investigate preparation of such states via parametric down conversion with femtosecond pump pulses.
	Quantum state estimation Optical quantum communication and measurements require often complete quantum state estimation. Our minimal polarimeter topologies allow efficient tomography of single and multiphoton states.