12 July 2011 New ICFO PhD graduate

Dr. Sibylle Braungardt

Thesis Committee

Dr. Sibylle Braungardt graduated with a thesis on complex quantum systems Dr. Braungardt graduated in Physics from the Technical University in Berlin, Germany. She started her PhD at ICFO in 2006 and during this time has been working in the field of complex quantum systems realized with trapped ions as well as atoms in optical lattices. She has studied the preparation, manipulation and detection of such systems.

Dr. Braungardt presented a thesis titled ‘Complex Systems for Quantum Technologies’. Her thesis was supervised by ICFO Group Leader and ICREA Prof. Maciej Lewenstein. Her co-advisor was Dr. Mirta Rodríguez Pinilla.


Complex systems provide advantages for the storage and processing of classical information. A well known example are neural networks, where error resistant information processing is achieved by storing the information in the stable states of the system. In quantum information, where error resistance is a major challenge, one can therefore expect that similar benefits arise. Within the work of the thesis, we address the question of whether complex quantum systems can provide advantages for the storage and processing of quantum information. As a first step, we develop a proof-of-principle implementation of a complex quantum system for quantum computation using a chain of ions in a trap. We show that error resistant quantum computation can be achieved by encoding the information in a distributed way in the energy levels of the system. However, due to the constraints in the number of ions that can be stored in the trap, the scalability to larger systems is limited. As a second step, we address the question of scalability.

Dr. Christian Trefzger, a former PhD student in the group, demonstrated that dipolar atoms or molecules in optical lattices provide a scalable system with many metastable states that could be used for quantum information tasks. The applicability of upcoming technologies using such metastable states requires appropriate detection methods for distinguishing them. We develop a method to characterize complex quantum systems in optical lattices by particle counting, allowing for the detection of different metastable states. Our results show that using the many-body features of quantum systems provides advantages for quantum information processing. We expect that a wide range of applications for quantum technologies can be developed by extending the concepts to scalable systems of dipolar atoms or molecules in optical lattices.


President: Prof. Michèle Leduc, Research Director Emeritus, CNRS - Kastler Brossel Laboratory, FRANCE
Secretary: Prof. Antonio Acín , ICFO-Institute of Photonic Sciences, SPAIN
Member: Prof. Roy J. Glauber, Nobel Laureate, Harvard University, USA