Ultracold quantum gases hover at temperatures close to zero Kelvin (-273 degrees Celsius), also called absolute zero because until recently it was thought to be the lowest possible temperature in the Universe. At absolute zero, particles stop moving completely and all disorder disappears. This system has become fertile ground for studies of quantum many-body systems, producing new insight virtually daily into the nature of the Universe. Scientists exploited laser-cooled, highly excited atoms (Rydberg atoms) to study particle interactions with EU funding of the project ‘Strongly correlated dipolar quantum gases with tuneable interactions in one-dimensional traps’ (1DDIPOLARGAS). Plasmas are the most prevalent phase of matter in the Universe. They are ionised atoms - mostly ions and free electrons. Although they are usually created by very high temperatures, photoionisation of laser-cooled atom clouds now does the trick, producing plasmas similar to those in very dense objects like the core of Jupiter. This makes them a window on the Universe in the laboratory. Project scientists discovered a new route to production of ultracold plasma that overcomes current limitations to the lowest temperatures achievable. It could pave the way to better understanding of the physics of the gas giants. Researchers also studied the formation of correlated systems of Rydberg aggregates composed of multiple Rydberg atoms. Applying statistical methods adopted from condensed matter physics, they opened a new window on the mechanism of formation and introduced a new way to study such systems. Additional work exploited electromagnetically-induced transparency (EIT), a quantum interference effect in confined light. Scientists extended the description of how atoms and light interact. They also developed a model EIT-based system for direct observation of energy transport important in photosynthetic systems directly applicable to understanding efficiency in light-harvesting photovoltaics. Further pioneering results open the door to studies of the transition from classical to quantum regimes in a precisely controlled way. Seminal studies exploiting ultracold gases during the project 1DDIPOLARGAS have enhanced the utility of such systems for both basic and applied research. From the fundamental nature of the Universe to applied photovoltaics, impact will be felt throughout the scientific community.
Gases, quantum, Ultracold, Rydberg, plasmas, correlated, electromagnetically-induced transparency, EIT