How to Trap Exactly One Molecule ✛
A laser beam focused to the size of a dust grain can hold a single molecule, just as tweezers hold a tiny bead. But filling a hundred such tweezers with exactly one molecule each is like trying to put a single drop of water into each compartment of an egg carton without spilling a drop. Typically, traps fill to only 20–50%, and extra molecules are quickly lost to collisions. The new work proposes a method that first makes molecules 'slippery' to each other, then gently pours off the extras, leaving exactly one particle in each trap.
Previously, there was no reliable way to leave exactly one molecule: traps filled only halfway, and extra particles were lost to collisions. Now it has been shown that a combination of static and microwave fields stabilizes the molecules and allows them to be controllably poured out, leaving one with accuracy above 99%. This result comes not from experiment but from a detailed theoretical calculation, yet it is based on real parameters of the NaCs molecule and existing laser technology. The method can be implemented in existing molecular tweezers setups.
The microwave field used for shielding has a frequency of about 6.2 GHz — close to the frequency of some Wi-Fi routers. But instead of transmitting data, it reshapes the interaction between molecules.