**July 15 2013**

**19.07.2013 Visit of Stefan Wißmann**

Stefan Wißmann visits us. He will give a presentation at 9:30, room 4.18 in building E2 6.

#### Quantum states with maximal memory effects and non-Markovian quantum probes

Perfect isolation of any quantum system is almost impossible to realize since it is usually influenced by the coupling to an environment. Typically, the interaction of the system with its environment cannot be neglected so that a modelling of a quantum physi- cal systems as a closed system fails to give a correct description of the system’s dynamics. The most prominent approach resorts to an approximation of the open system dynamics in terms of a so-called Markovian master equation which includes several rather drastic assumptions on the properties of the system and environment. It is not surprising that there exist complex systems for which this relatively simple description fails to give a faithful picture of the dynamics. Recently, there has been put much effort in developing a general theory and classifying non-Markovian open system dynamics. In my talk I summarize the basic principles of different approaches to quantify non-Markovian be- havior and present the latest results on the non-Markovianity measure proposed in [1] regarding the mathematical and physical properties of optimal pairs maximizing this quantity [2]. Moreover, I show some interesting applications how non-Markovian open system dynamics can be used as a probe for environmental properties [3, 4].

##### References

[1] Breuer, H.-P., Laine, E.-M. and Piilo, J. Measure for the degree of non-Markovian behavior of quantum processes in open systems. Phys. Rev. Lett. 103, 210401 (2009).

[2] Wißmann, S., Karlsson, A., Laine, E.-M., Piilo, J. and Breuer, H.-P. Optimal state pairs for non-Markovian quantum dynamics. Phys. Rev. A 86, 062108 (2012).

[3] Haikka, P., McEndoo, S. and Maniscalco, S. Non-Markovian probes in ultracold gases. Phys. Rev. A 87, 012127 (2013).

[4] Borrelli, M., Haikka, P., De Chiara, G. and Maniscalco, S. Non-markovian qubit dynamics induced by coulomb crystals. Phys. Rev. A 88, 010101 (2013).