“Three-dimensional Rydberg polaritonics in the quantum regime”
OPUS grant 2024/53/B/ST2/04040 is funded by the National Science Centre, Poland.
PI: Michał Parniak
Grant amount: 2 249 802 PLN
Project duration: 4 years (January 2025 — January 2029)
Project description:
Polaritons are quasi-particles known to be a superposition of material excitations and optical photons. Polaritons are well-known to occur in both condensed matter and atomic systems. While polaritons are of interest even in the single-particle picture, many interesting phenomena emerge from the interaction between polaritons. In condensed matter systems, these interactions are inherent, whereas, in atomic systems, they can be controlled through various parameters such as external fields, selection of atomic levels (in particular Rydberg states), and proper optical addressing. Currently, there is great interest in polaritonic systems involving exciton-polaritons in materials such as cuprous oxide or 2D materials, Cooper-pair polaritons in superconductors, or phonon polaritons in topological insulators. In atomic systems, polaritons have been observed in slow light effects in both hot and cold atomic gases, including Bose-Einstein condensates (BECs). Of particular interest are Rydberg polaritons, for which strong mutually strong coupling can be achieved. These interactions enable the effective interaction between photons, which typically only interact at extremely high fields. Rydberg polaritons hold promise for the creation of quantum gates between single photons. However, experiments so far have been limited to studying polaritons in 0D or 1D. The most popular system for studying Rydberg polaritons is a long atomic cloud, where interactions between polaritons living in 1D space can be explored. Additionally, the atomic sample can be confined to the volume smaller than the Rydberg blockade, and with the help of an optical cavity that strongly confines the optical field, the polaritonic system can be effectively reduced to zero dimensions. Such a system is also known as a Rydberg quantum dot. In our project, we plan to explore interactions of Rydberg polaritons in three and two dimensions. The higher dimensionality of the system will allow for the observation of previously unexplored effects. This exploration takes a different direction compared to most experiments, which focus on involving more particles and studying many-body physics in 0D or 1D samples. Our proposal expands the dimensionality of the polaritonic system and, therefore, holds the potential to study the interaction of more particles in an easier way. With higher dimensionality, we expect to have greater control over the dispersion relation of the polaritons. Specifically, we can engineer the interaction such that the mass of the polariton changes as a function of the reciprocal space direction, potentially leading to the density of states singularities similar to electronic systems in condensed matter physics. In two and three-dimensional systems, the existence of bound states is more complex, and we may observe effects arising from the emergence of particular bound states as a function of interaction strength and the shape of the polariton dispersion, such as the recently discovered vortices in bipolariton wavefunction. To engineer the proposed interaction, we will use a shaped atomic ensemble prepared using a dipole trap and a set of laser beams. These will define the geometry of the system and allow us to create and understand the dispersion relation in the spatial domain. We will control electromagnetically induced transparency (EIT) effects as a function of position within the ensemble. We will also use our capacity to excite atoms to different Rydberg states to observe interactions between polaritons e.g. in S and P orbital states. One of the major obstacles for studies in higher dimensions has been the issue of detection. To overcome this, we will employ state-of-the-art custom methods, including both time and space-resolved single-photon camera detectors, as well as mode-projection-based detectors based on photon counters and spatial light modulators (SLM). Those novel techniques will overall enable the discovery of previously unobserved polariton physics. As mentioned, one of the significant impacts of this project could be the ease of exploring the interactions of many particles, towards the various forms of polaritonic quasi-chemistry. One notable example for which more than 1D system is needed that we plan to explore is the observation of an Efimov state of three polaritons, without the existence of two-polariton bound states.