Researchers have generated a Bose-Einstein condensate aboard a rocket, which is an important step in designing extremely accurate gravitational wave sensors.These condensates are not an invention of solitary library mice. They were proposed in 1925 and, when technology finally advanced enough, they became reality for the first time in 1995. Now, thanks to the latest advances, scientists have managed for the first time to create a Bose-Einstein condensate in space, on board a rocket. The authors, led by Maike Lachmann and Ernst Rasel, researchers at the University of Hanover (Germany), have made 110 measurements in which they have demonstrated the enormous potential of these condensates in space to create extremely sensitive gravitational wave sensors and for open a whole new field that is about to be explored. Their findings have been published in Nature.
The researchers designed a platform, the size of a person, inside which a group of atoms was trapped on a chip. A rocket, launched from Sweden, on January 23, 2017, raised this platform to 243 kilometers in height. The trajectory provided six minutes of microgravity, in which the device created a Bose-Einstein condensate, for 1.6 seconds and composed of 105 atoms, and made dozens of measurements on its state.
What is the purpose of these experiments? To understand it, we must bear in mind that Bose-Einstein condensates generate a very dense quantum state, which is very sensitive to very small inertial forces. Therefore, these condensates are suitable for measuring very small accelerations. This has already been carried out in laboratories on land, but if it is carried into space, in a microgravity environment, the sensibility of these sensors is multiplied.
The Bose-Einstein condensates are based on the wave-corpuscle duality, which describes the elementary particles in terms of waves of quantum mechanics called Broglie waves. It turns out that the higher the velocity of a particle – that is, the higher the temperature at which it is – the shorter the wavelength of that wave. Therefore, a cloud of hot atoms have short Broglie waves and each can be considered as an individual object.
But, if the atoms are cooled to a threshold, the wavelengths increase so much that they cover the entire cloud of atoms, so that the particles condense in a state in which they all behave in the same way, and can considered as members of the same wave of matter: it is the Bose-Einstein condensate. The interesting thing about this state is that its matter waves can be used to make measurements through interferometry techniques. What does this mean? A laser light separates these waves and then recombines them, producing concrete and stable patterns of interference. But if there are external distortions, for example generated by a gravitational wave or a change in temperature, the system detects variations with great sensitivity.
Dennis Becker et al. 2018. Space-borne Bose–Einstein condensation for precision interferometry. Nature. DOI: 10.1038/s41586-018-0605-1