The first condensate of molecules

Physicists have been able to make condensates with atoms for 30 years. And they had been trying with molecules for 10 years. That’s it: here is the first Bose-Einstein condensate made up of 1000 molecules.

Hervé Poirier, editor-in-chief of the scientific magazine Epsiloon tells us about the first “molecular Bose-Einstein condensate”. It’s a bit scary to say it like that…

franceinfo: What is it about?

Hervé Poirier: It’s actually fairly easy. And quite fascinating: it shows the extravagance of the world we live in. These are very simple molecules, made up of two atoms, one of sodium and one of cesium. There are 1000 of them like that: a sort of mini-gas. American physicists have achieved the feat of transforming these 1000 distinct entities into a single material object.

Physically speaking, the molecules are no longer separated. They literally melted together, into a stable and coherent entity: a condensate. A bit like a disorderly crowd that suddenly starts moving in unison. Based on quantum equations, Albert Einstein and the Indian physicist Satyendranath Bose predicted, in 1925, that such a phenomenon was possible.

We had to wait until the 90s to succeed in performing this magic trick, with atoms. There, it is with more structured matter: molecules. It’s much more difficult – these physicists have been trying for 10 years. And it’s even more impressive.

How did they achieve this quantum feat?

Here, it must be recognized that it is a little more technical. The principle is to cool the molecules sufficiently so that the uncertainty in their respective positions – an intrinsic characteristic of quantum objects – becomes greater than the distance which separates them. In theory, the molecules then become indistinguishable. In practice, they transform into a Bose-Einstein condensate.

The team of physicists here applied subtle magnetic fields to cool them to 6 billionths of a degree, above absolute zero, preventing these molecules from colliding – which could cause unwanted chemical reactions. And pop! It was clear and unmistakable. There were no longer 1000 molecules in the box, but only one condensate.

Very pretty, but what’s the point of all this?

The interest is that the condensate displays well-controlled quantum behavior, but on a macroscopic scale. This makes it possible to envisage ultrasensitive sensors, hyperprecise clocks, quantum computers. It can also be used to study exotic phenomena or the behavior of black holes.

Above all, this shows us, if it were still necessary, that we definitely live in a strange world. We’ve known this for exactly 100 years. But we still have difficulty achieving it.