Experimental apparatus for the production of a degenerate gas of polar molecules

A round glass cell (centre, in black frame) is designed to hold a gas of molecules cooled to 50 billionths of a Kelvin. Caption: Ye Group/Steven Burrows/JILA

Quantum physics

A superchilled molecular gas nears the quantum limit of coldness

Long-sought molecular state promises to help scientists unveil quantum-scale chemistry.

After a decade of attempts in labs around the world, researchers have succeeded in making a gas of molecules so cold that they bump up against the limits of quantum physics.

Gases composed of individual atoms can be supercooled until quantum effects — the strange behaviours of very small particles — prevent the atoms from shedding more energy. But it’s much harder to make this sort of gas using molecules, which are structurally more complex than atoms and, as a result, are more able to retain movement and energy.

Jun Ye and his team at the University of Colorado Boulder cooled millions of individual rubidium and potassium atoms until they approached the quantum limits of coldness. The researchers then used a magnetic field and light pulses to bind the atoms into a gas comprising tens of thousands of molecules at temperatures of 50 billionths of a Kelvin, well below the threshold at which quantum effects dominate.

Studies of such molecular gases could provide fresh insight into chemistry at the quantum scale, the authors write.