Wochenübersicht

Rydberg Atoms in highly excited electronic states with n=30-100 are recent additions to the versatile toolkit of ultracold atomic physics. At rest, treated as a "frozen gas", they hold promise for applications well beyond atomic physics and serve as experimentally accessible interacting many-body systems for quantum information and in condensed matter physics. While for those applications the residual atomic motion is usually an unavoidable perturbation and source of noise, we will make use of this motion for preserving coherent electron dynamics, very much like in molecules, but for transport instead of stationary states [1]. In Rydberg atoms, accelerated via dipole-dipole interactions, we find an intricate link between atomic motion and the transport of electronic excitation energy. This link allows one to realize adiabatic exciton transport schemes and system potential energy landscapes that mimick those of relevance for quantum chemistry [2]. The analogy between the chemical energy surfaces and those among Rydberg atoms will enable more detailed studies of quantum many-body dynamics on these surfaces. On shorter time scales where atomic motion is no longer crucial, a system of a few interacting Rydberg atoms shows parallels to energy transport in photosynthetic light harvesting complexes. Consequently, it provides a transparent analog for the quantum simulation of the latter [3]. In particular, by embedding the assembly of Rydberg atoms into a background atomic gas, crucial but complex features in light harvesting systems, such as disorder and decoherence can be introduced in a controlled manner. Finally the two features can be combined, to investigate the effect of controllable decoherence on Rydberg motion [4], or the effect of impurity motion onto a condensed environment [5]. [1] S. Wüster and J.M. Rost JPB 51, 032001 (2018). [2] S. Wüster, A. Eisfeld and J. M. Rost , PRL 106, 153002 (2011). [3] D. Schönleber et al. PRL 114 123005 (2015). [4] S. Wüster, PRL 119 013001 (2017). [5] S. Tiwari and S. Wüster, PRA 99 043616 (2019).

Scattering amplitudes form a bridge connecting theoretical particle physics with the real world of collider experiments, yet their computation by means of Feynman diagrams quickly becomes prohibitive. Focusing on the simplest case of N=4 super Yang–Mills theory, in this talk I present recent progress in bypassing these limitations and directly constructing amplitudes, by exploiting their expected analytic structure. First, I describe the discovery of new, possibly universal analytic properties known as the extended Steinmann relations, or equivalently cluster adjacency, as well as the coaction principle. Then, I demonstrate their power in computing the six-particle amplitude up to seven loops, as well as the seven-particle amplitude up to four loops, and discuss further applications.

Optical wavefront shaping by means of spatial light modulators (SLMs) based on liquid crystal (LC) panels, has become a powerful tool in Biophotonics. “Holographic optical tweezers” are well-known and widespread, but an SLM can also be integrated into optical imaging systems. This makes the microscope programmable and adaptable with respect to the needs of a specific sample. A particular strength of the Synthetic Holography approach with programmable phase masks is the possibility to multiplex, which means that one can ‘pack’ several tasks into one computer-generated hologram. One can, for instance, create images which are composed of sub-images belonging to different microscopy modalities, to different depths inside the volumetric sample, or to different parameter settings. Moreover, if the phase modulation range is not restricted to 2π, the wealth of possibilities significantly increases: Several computer-generated holograms can be read out at different wavelengths from one and the same input pattern sent to the LC panel. In this way holographically modified imaging in the visible can be accommodated in the same phase mask that is used for holographically controlled trapping in the near-infrared.

The combination of electromagnetically induced transparency (EIT) and strongly interacting atomic states in optical media has opened up new routes towards achieving few-photon optical nonlinearities. While EIT provides strong light-matter coupling under low-loss conditions, the interactions between such Rydberg states can be used to generate nonlinearities that are large enough to operate on the level of single photons. Such synthetic interactions promise few-photon applications and exotic many-body physics, emerging from the interplay of coherent driving, quantum light propagation, strong atomic interactions and dissipative photon scattering. This talk will present basic concepts underlying this approach and discuss simple examples that afford an intuitive understanding. Placing particular emphasis on many-body decoherence processes we will identify challenges but also new opportunities for generating and manipulating nonclassical states of light. Finally, we will consider new ideas beyond traditional Rydberg-EIT approaches as well as new platforms beyond ultracold atomic ensembles.