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

Abstract: Controlling quantum behavior of light and matter is an outstanding challenge in modern science and engineering. It is at the heart of many modern developments in an emerging interface involving quantum optics and quantum information science, mesoscopic physics, nano-science and many-body physics of strongly correlated systems. Two examples of these developments, will be described in this talk. Specifically, we will discuss our recent work involving the controlled manipulation of individual nuclear spins in a high-purity diamond lattice. Our approach combines ideas from single molecule spectroscopy, quantum optical control techniques and the physics of mesoscopic spin ensembles. It allows us to isolate, polarize and manipulate single nuclear spins and use them to create quantum memory and small quantum registers with exceptional coherence properties, even under ambient room temperature conditions. We will also describe a novel approach to controlling light-matter interactions that make use of sub-wavelength localization of optical fields on metallic nano-sized wires. This approach combines the ideas of quantum optics with those of electronics and plasmonics. We show that it can be used to create an efficient quantum interface between individual optical emitters and individual surfaces plasmons. Looking forward, we will describe novel applications of these techniques. These include single photon nonlinear optics and strongly interacting many-body systems of photons, new approaches to quantum communication and computation as well as new quantum magnetic sensors with nanoscale resolution. [more]
Abstract: Quantum coherence effects such as electromagnetically induced transparency can be used for a multitude of linear and nonlinear optics. I will introduce two novel applications in order to demonstrate potential uses of these ideas: First, how to electromagnetically induce chirality and how to use it to create media with negative refraction, as needed, for example, for the so-called "superlens"? Second, how can one utilize the long-range interaction of dipolar molecules to create a quantum computer based on either single particles or molecular ensembles? [more]
Abstract: When two atoms scatter off one another, they temporarily populate molecular bound states. Usually this happens with rather low probability but this process can be resonantly enhanced by applying a static magnetic field. We experimentally study this process with an unusual boundary condition, namely in an optical lattice where each lattice site is occupied by exactly two atoms which in some sense permanently scatter off each other. Here, the application of the magnetic field leads to sinusoidal oscillations between the atomic and the molecular state during which a molecule fraction of almost 100% is reached. [more]
Abstract: We demonstrate a new method of investigating optical field ionized (OFI) plasmas which allows their dynamics to be studied with ultrahigh temporal resolution and yields information not accessible by other methods. Ultrashort electron pulses with an energy of 20 keV are directed onto an OFI nitrogen plasma generated by a 50 fs titanium-sapphire laser pulse. Deflection of the electrons by the fields resulting from charge separation yields images of the expanding plasma. Pump-probe experiments of the plasma expansion capture changes within a few picoseconds with high spatial resolution. Analysis of the images reveals features not seen in previous studies: an expanding cloud of relatively hot electrons and electron lobes at the entrance and exit of the laser. [more]
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