The big deal about small molecules

One of the biggest ways for science to impact people’s lives is to discover new materials, which can be used to harness the sun’s energy more efficiently, develop wearable medical sensors for better healthcare delivery, etc. It turns out that while many interesting materials have already been discovered (like superconductors, which transport electricity without any loss), scientists do not really understand what is going on at the microscopic level, making it difficult to create or engineer new materials with ideal properties.

One way scientists have pursued to understand materials is to model them using computers. However, it turns out that for some materials, there are strong interactions between the microscopic particles, which also obey the laws of quantum mechanics. The combination of strong interactions and quantum mechanics makes it difficult if not impossible for computers to calculate their behavior. To get around the problem, we turn to the building blocks of the physical world – atoms and molecules.

Atoms and molecules tend to behave in weird ways described by the laws of quantum mechanics. For a few decades, physicists have managed to cool and control atoms using lasers. By doing so, the atoms have been shown to exhibit quantum behavior. The trick to understanding new materials, then, is to set up these atoms to obey the same equations as those we use to model the materials, except that we now have arbitrary control over their quantum properties at the microscopic level! This approach has spawned a hot field of research: quantum simulation with atoms.

Molecules, on the other hand, offer more “knobs” than atoms. Unlike atoms, molecules can vibrate and rotate, so they have a much larger set of quantum states. The large set of quantum states has made it challenging for physicists to cool and control molecules using lasers. However, recent research developments have now made it possible to work with cold and ultracold molecules in a single spin state. The lure of molecules is that they can behave like magnets, whose interactions are generally richer compared to the interactions between atoms. If atoms are like “quantum legos”, molecules are like “quantum playdoh”, whose size and shape you can dynamically change. Wow, imagine what dream materials you can now assemble with such versatile building blocks!

Cold and ultracold molecules promise to impact our understanding of the world in more ways than modeling materials.¬†They have already been used to study cold controlled chemical reactions and to probe fundamental physics questions related to why there is way more matter than anti-matter in the universe (read: “why do we exist?”). Ultracold molecules have also been recently demonstrated to have long lived spin coherence times, which means that they are potentially good candidates for storing bits of information in quantum computers. More results will be forthcoming from the molecular physics community. Stay tuned!