On the solution of the Bogolyubov chain for a van der Waals' crystal

Hashem Zoubi, Alexander Eisfeld, Sebastian Wüster

Assemblies of Rydberg atoms subject to resonant dipole-dipole interactions exhibit Frenkel excitons. We show that van der Waals shifts can significantly modify the exciton wave function, whenever atoms approach each other closely. As a result, attractive dipole-dipole potentials and repulsive van der Waals interactions can be combined to form stable one-dimensional atom chains, akin to bound aggregates. Here the van der Waals shifts ensure a stronger homogeneous delocalization of a single excitation over the whole chain, enabling it to bind several atoms. When brought into unstable configurations, such Rydberg aggregates allow the direct monitoring of their dissociation dynamics.

И.П. Базаров

Edward V. Gevorkyan

Qiangbing Guo, Yunkun Wu, Di Zhang +5 more

Polarization entanglement holds significant importance for photonic quantum technologies. Recently emerging subwavelength nonlinear quantum light sources, e.g., GaP and LiNbO3 thin films, benefiting from the relaxed phase-matching constraints and volume confinement, have shown intriguing properties, such as high-dimensional hyperentanglement and robust entanglement anti-degradation. Van der Waals (vdW) NbOCl2 crystal, with strong optical nonlinearities, has emerged as a potential candidate for ultrathin quantum light sources. However, polarization entanglement is inaccessible in the NbOCl2 crystal due to its unfavorable nonlinear susceptibility tensor. Here, by leveraging the twist-stacking degree of freedom inherently in vdW systems, we showcase the preparation of polarization entanglement and quantum Bell states. Van der Waals NbOCl2 crystal is a candidate platform for subwavelength thin film photon-pair sources. Here, the authors demonstrate generation of polarization entangled states from a two-layer stack of orthogonally oriented van der Waals crystal.

George P. Flessas

D. Ciampini

Van der Waals interactions between ultracold atoms excited to high-lying Rydberg states can lead to \nstrongly correlated excitation dynamics [1]. In my talk I will present a direct observation in real space \nof the mechanical effect of the van der Waals force on individual Rydberg atoms excited at close range \n[2]. Clusters of Rydberg atoms are created by first generating a small number of seed excitations in a \nmagneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation \nevents. Our experimental results agree well with a numerical simulation of the van der Waals explosion.