Colloquia


Colloquia

Due to the current situation (COVID-19), the guest lectures of the MPQ Colloquium will only take place online until further notice. Details on participation will be sent via the mailing lists [wiss-mpq] and [Mpq-colloquium-stream]. Please register using the adjacent link.


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

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Room: Herbert-Walther Hörsaal
Like all nanostructures, carbon nanotubes have interesting electromagnetic properties in the near field. The electromagnetic field near the cylindrical nanotube surface is affected by the electronic band structure, surface conductivity, and surface curvature of the nanotube. As a result, the interactions between the surface electromagnetic modes of the nanotube and, say, a surface excitonic state, or an atom (ion, molecule) doped into the nanotube have specific behaviors that have not been deeply explored thus far. [more]
Integrated optic devices – such as optical fibers, waveguides or linear optical circuits – in combination with pulsed quantum light and time-multiplexing configurations offer distinct advantages to realize photonic quantum systems for quantum information applications. The experimental setups get miniaturized, the spatial properties of generated quantum states are defined by the guiding geometries and networks are intrinsically stable. We present our toolbox for the realization of future quantum devices, including engineered genuine single-mode pulsed quantum light and a high dimensional quantum walk experiment. [more]
Diamond is not only the king gemstone, but also a promising material in modern technology (which holds a promise to replace silicon) owing tounprecedented thermal conductivity, high charge carrier mobility and chemical inertness. Less known is that defects in diamond can be used for quantum information processing. Owing to their remarkable stability, colour centers in diamond have already found an application in quantum cryptography. Furthermore, it was shown that spin states associated with single nitrogen-vacancy defects can be detected optically. In this talk I will discuss recent progress regarding spin-based quantum information processing and atomic magnetometry using single spins in diamond. [more]
On a sub-wavelength scale, atoms in a crystal, i. e. an ordered lattice, are normally assumed to be almost uniformly excited by an incident light. An interatomic interaction produces then a uniform local field (different from that of incident laser) at each atom as well. This is a major assumption in the Lorentz-Lorenz theory of interaction of light with dense matter. We showed [1] that at certain critical conditions on the atomic density and dipole strength, a previously unexpected phenomenon emerges: the interacting atoms break the uniformity of interaction, and in a violent switch to a strong non-uniformity, their excitation and local field form nanoscale strata with a spatial period much shorter than that of laser wavelength, thus changing the entire paradigm of light-matter interaction. The most interesting effects can be observed for relatively small 1D-arrays or 2D lattices if the laser is almost resonant to an atomic quantum transition. The effects include huge local field enhancement at size-related resonances at the frequencies near the atomic line, so that the strata are readily controlled by laser tuning. A striking feature is that for the shortest strata, the nearest atomic dipoles counter-oscillate, which is reminiscent of anti-ferromagnetism of magnetic dipoles in Ising model. [more]
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