Colloquia


Colloquia

We plan to return partly to in-person talks. These talks will be held in the interim lecture hall B 0.32 at MPQ and can additionally be attended online. Some talks remain online only.

2G regulations apply to in-person talks, i.e. every time you wish to participate in person, you will have to prove, e.g. with the CovPass-App, that you are vaccinated or recovered.Whether facemasks have to be worn inside the lecture hall will be communicated in the the e-mail announcement for each talk separately. In any case, you will need a medical facemask in the hallway. Audience not affiliated with MPQ are welcome to join in person as long as they meet 2G criteria.

Details on how to participate online are distributed via the mailing lists [wiss-mpq] and [Mpq-colloquium-stream]. To receive this information, please register using the adjacent link.

Scientific organization of the talks:  Dr. Stephan Dürr and Dr. Thomas Udem

Quantum control of light and matter is an outstanding challenge in modern science. Diamond-based materials have recently emerged as a unique platform for quantum science and engineering [1]. Spins of single Nitrogen-Vacancy (N-V) color centers in diamond can be imaged, initialized and read out optically, and show quantum coherence even at room temperature. Full control over the spin state and the optical transition may enable exciting applications such as long-distance quantum teleportation and quantum information processing. Moreover, the tunable interactions of the NV center with its environment also make this system an excellent test bed for fundamental studies on decoherence, spin-bath interactions, and light-matter interactions in engineered nanostructures.In this talk I will present our latest results on schemes to protect single-spin coherence from the surrounding spin bath [2] as well as quantum control of the spin bath itself. Also, I will discuss our progress towards entanglement of distant NV center spins via photon interference [3].[1] Ronald Hanson and David D. Awschalom, Nature 453, 1043 (2008).[2] G. de Lange et al., Science 330, 60 (2010).[3] L. Robledo et al., Phys. Rev. Lett. 105, 177403 (2010); T. van der Sar et al., arXiv:1008.4097 (2010). [more]
The second law of thermodynamics presupposes a clear-cut distinction between the controllable and uncontrollable degrees of freedom by means of macroscopic operations. The cutting-edge technologies in quantum information and nano-science seem to force us to abandon such a notion in favor of the distinction between the accessible and inaccessible degrees of freedom. In this talk, I will discuss the implications of this paradigm shift by focusing on how the second law of thermodynamics can be generalized in the presence of a feedback control [1]. I will also discuss the minimum work required for measurement and erasure of information [2]. The Jarzynski equality has to be generalized in the presence of feedback control [3], as confirmed experimentally using polystyrene beads [4]. References[1] T. Sagawa and M. Ueda, Phys. Rev. Lett. 100, 080403 (2008).[2] T. Sagawa and M. Ueda, Phys. Rev. Lett. 102, 250602 (2009).[3] T. Sagawa and M. Ueda, Phys. Rev. Lett. 104, 090602 (2010).[4] S. Toyabe, T. Sagawa, M. Ueda, E. Muneyuki, and M. Sano, to appear in Nature Physics, arXiv:1009.5287 (2010). [more]
In the recent years ultracold atomic gases have been used to probe some fundamental questions in Many-body Physics. Thanks to the high degree of control of cold atoms using laser fields and magnetic fields, new insights on key problems from condensed matter systems has been gained. In this talk, we will provide one such example through the measurement of the equation of state of strongly interacting Fermi gases [1,2]. The tunability of the interaction between atoms enables one to connect the regime of superfluidity of weakly bound Cooper pairs described by BCS theory to the regime of strongly bound molecular pairs forming a Bose-Einstein condensate. The phase diagram of the dilute Fermi gas has been established experimentally and comparison with advanced many-body theories has revealed several surprises. Our equation of state can be directly used to describe the outer shell of neutron stars despite of 24 orders of magnitude difference in matter density and 14 orders of magnitude in temperature. [1] S. Nascimbène, N. Navon, K. J. Jiang, F. Chevy, and C. Salomon, Exploring the thermodynamics of a universal Fermi gas, arXiv:0911.0747, Nature, 463, 1057 (2010) [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, The Equation of State of a Low Temperature Fermi Gas with Tunable Interaction, Science328, 729 (2010) [more]
We present a new source of cold paramagnetic atoms and molecules. The paramagnetic particles are cooled during the adiabatic expansion and become entrained in an intense, cold but fast supersonic beam. We efficiently decelerate the paramagnetic particles by trapping them in a co-moving decelerating magnetic trap. Since the particles remain trapped in three dimensions during the deceleration process our method is capable of achieving higher densities limited only by the initial density of a supersonic beam. We present our first results on deceleration in a moving magnetic trap by bringing metastable Neon atoms to near rest. [more]
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