Quantum gases of molecules are created by cooling to nanokelvin temperatures, only 0.000 000 001 degrees above absolute zero. Under these conditions, quantum effects dominate and the molecules behave collectively, forming a Bose-Einstein condensate in which many molecules share the same quantum state. This new artificial quantum matter acts as controllable model materials that allow researchers to study quantum behavior relevant to electrons in real materials.
Collisional loss
But unlike electrons in real materials, the molecules in these artificial quantum systems are easily lost when they collide. For ultracold molecules, collisional loss is extremely rapid and occurs in essentially every close encounter. Reseacher Tijn Karman says: ‘By controlling the molecular dipole moments with microwaves, researchers were able to suppress these losses by more than a factor 10,000. In fact, the suppression was so great that only an upper bound, set by the single-molecule lifetime, could be measured in the lab of Sebastian Will (Columbia).’
From quantum gas to quantum liquid
Reducing collisional loss allows researchers to create denser and more stable molecular gases. At the same time, the microwave control induces strong, long-range interactions between molecules. Karman: ‘This combination makes it possible to realize stable quantum liquids, where the interaction range is larger than the average distance between molecules. Such systems provide a new platform for exploring strongly interacting quantum matter that is difficult to achieve with atomic gases.’
A week earlier Karman published an article about how he was able to create highly ordered arrays of molecules: almost like molecules in an egg carton. Such ordered molecular arrays could provide a foundation for scaling up experiments with molecules as quantum bits.