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German scientists produce first Bose-Einstein condensate with calcium atoms

Submitted by on 29 October, 2018 – 4:32 pm
Like a giant wave in a sea of gaseous calcium atoms, the Bose-Einstein condensate rises. It consists of approx. 20 000 atoms that are not normally visible to the human eye. However, the waves describing the quantum mechanics of atoms, all oscillate synchronously in the condensate and accumulate to form a dense tidal wave. Thus, the atoms pile microscopic and macroscopic suddenly becomes so visible.

Physicists at the Physikalisch-Technische Bundesanstalt (Germany) have succeeded in producing a Bose-Einstein calcium alkaline earth element. The use of alkali atoms creates a new potential for precision measurements, eg for the determination of the gravitational fields.

The physicist and Nobel laureate Wolfgang Ketterle once described as an “identity crisis” of atoms: If the atoms are trapped in a trap and cooled to a temperature close to absolute zero point, condense – similar to that of water vapor – and have the status of a new whole: They become indistinguishable. This condition is called collective – named for its intellectual father – Bose-Einstein condensate.

Physicists at the Physikalisch-Technische Bundesanstalt (PTB), which have succeeded for the first time in the world in producing a Bose-Einstein condensate of calcium alkaline earth element. The use of alkali atoms creates a new potential for precision measurements, eg for the determination of the gravitational fields. Because unlike previous Bose-Einstein alkali atoms, alkali metals react a million times more responsible with the fact wavelength of optical excitations – one that can be used for super accurate measurements. Theresults have been published in Physical Review Letters.

Quantum mechanics background

The gas atoms at room temperature behave like a wild bunch: they fly in droves at different speeds, collide, and then swung back the other way. However, at extremely low temperatures near absolute zero point zero degrees Kelvin (-273.15 degrees Celsius) to almost come to a standstill. At this point, the laws of quantum mechanics come into force and these can not be observed in everyday life and have a destabilizing effect on many non-physical. The idea of atoms as tiny spheres does not work any longer. In fact, the atoms can now only be described by the waves of quantum mechanics. As waves of water that can overlap each other. In the case of a Bose-Einstein condensate, the wave functions up to a million atoms are so synchronized that are stacked to form a giant wave. These formations can grow to a millimeter in size and can then be photographed. The microcosm is presented macroscopically – becomes visible to the observer. In recent years, such Bose-Einstein have been used for various research on the foundations of quantum mechanics as a model system for solids, or quantum information.

Potential applications

The wave patterns of Bose-Einstein condensates are very excited sensitive to their surroundings. Thus, by investigating these patterns, it is possible to produce highly sensitive interferometric sensors, for example, that magnetic fields but also for gravitation. For handling und condensate excitation light is used. All Bose-Einstein condensates produced so far around the world have a common disadvantage: their large optical transitions do not allow precision excitations. In the case of Bose-Einstein condensates of alkali atoms (eg, calcium and strontium, both of which are being investigated at PTB as to their suitability as optical clocks) of its super-narrow Transitions Optical offers new possibilities for investigations of accuracy. Conceivable use in satellites, for example, by geophysicists who study the deformation of the Earth and therefore the change in gravity.


In PTB was possible for the first time in the world to produce a Bose-Einstein condensate of alkali atoms. To this end, 2.106 calcium atoms precooled in a magneto-optical trap loaded at a temperature of 20μK in optical tweezers. Due to the weakening of the force that holds the hot atoms are vaporized, which are cooled by the remaining atoms. A normal temperature of 200 nK is the critical temperature is reached with 105 atoms. Of these, approximately. 2.104 atoms can be cooled to form a pure condensate.

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