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A new form of matter

Artist's impression of an atom cloud at the crossing of laser beams created in outer space

Image: KW NEUN

In 1995, a former physics student of the Technical University of Munich (TUM) accomplished something that Albert Einstein had once predicted. At ultra-cold temperatures – almost absolute zero – Wolfgang Ketterle succeeded in generating a new state of matter: a quantum gas. In 2001 he was awarded the Nobel Prize for his achievement.

The quantum gas – a new state of matter

It finally happened on the night of September 29, 1995: A dark spot appeared on the computer screen in Wolfgang Ketterle’s physics laboratory at the Massachusetts Institute of Technology (MIT) and the shadow of the atom cloud became gradually more and more distinct. Ketterle and his team worked right through the night, and by morning it was clear: They had succeeded in changing sodium atoms into a new physical state. And they accomplished this at the lowest temperatures ever generated: just below a microkelvin – less than a millionth of a degree above absolute zero.

At this ultra-cold temperature, atoms that were previously independent meld into a single quantum state and formed a “quantum gas”, as Ketterle called this new state of matter. Individual particles can no longer be distinguished because they have formed a single macroscopic matter wave. Albert Einstein predicted this phenomenon of quantum physics as early as 1924, based on a previous paper by his Indian colleague, Satyendra Nath Bose, on photon statisitcs. However, experts long considered it virtually impossible to actually produce such a Bose-Einstein condensate (BEC).

But that is precisely what Ketterle managed to do – and was thus awarded the Nobel Prize in Physics in 2001, together with Eric Cornell and Carl Wieman. These two were a few months ahead in the race to produce a quantum gas but Ketterle’s team united significantly more atoms in their BEC, while also making fundamental discoveries about the quantum mechanical properties of this new form of matter.

“When a gas consisting of uncoordinated atoms turns into a Bose-Einstein condensate, it is like when the various instruments of an orchestra with their different tones and timbres, after warming up individually, all join in the same tone .”

Nobelpreis-Medaille

Prof. Sune Svanberg, 2001, Royal Swedish Academy of Sciences, Presentation Speech for the Nobel Prize in Physics

Bild: © ®The Nobel Foundation: Photo: Lovis Engblom

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