Cool effort MIT-Harvard Center for Ultracold Atoms

Call it the big chill. Laser cooling has tackled its biggest molecule yet, bringing the temperature of a three-atom molecule to within a thousandth of a kelvin of absolute zero for the first time. The feat could eventually be used to build molecular quantum computers.

Physicists have been laser cooling individual atoms since the 1970s, but it’s much harder to apply it to molecules. The technique works by causing an electron bound to the atom (or molecule) to release photons, which relies on matching the system’s energy levels with those of the cooling lasers. The more atoms a molecule contains, the more complex its vibrations and rotations, making it difficult to achieve a match.

Ivan Kozyryev and his team at the MIT-Harvard Center for Ultracold Atoms have now managed to use lasers to cool molecules of strontium monohydroxide. Now that his team has shown it works with three-atom molecules, Kozyryev thinks the technique could be extended to molecules with up to around 15 atoms.


Such ultra-cool molecules could form the basis of molecular quantum computers, he says. “You can actually use laser light not only to cool atomic molecules but to redial their state precisely.” If physicists can control which parts of a molecule are vibrating, they could use this technique to store information.

Cooling molecules to such low temperatures is extremely tricky, so these results are impressive, says Vincent Boyer at the University of Birmingham, UK. But Boyer does not expect it to lead to molecular quantum computers in the near future as progress in this area has been so slow. “We’re not going to get laser-cooled complex molecules any time soon,” he says.

However, the technique could also be useful to chemists, says Boyer. Molecules cooled close to absolute zero would react much more slowly, potentially allowing researchers to observe reactions at much greater levels of detail than currently possible, he says.

Journal reference: Physical Review Letters, DOI: 10.1103/PhysRevLett.118.173201