IT鈥橲 the world鈥檚 smallest trampoline. Bouncing atoms with lasers could make ultra-precise measurements of gravity.
To test theories such as general relativity, the strength of gravity is measured precisely using ensembles of supercold atoms falling in a vacuum chamber. These ensembles are called 鈥溾��. BECs act in a quantum-mechanical wave-like fashion and interfere with each other. The interference pattern depends on the paths the atoms take, so gravity鈥檚 effect on how fast they fall can be calculated by analysing the pattern with an interferometer. The longer the fall, the more precise the measurement 鈥� but the harder it is to keep the ensemble intact.
Now Philippe Bouyer of the Institute of Optics in Palaiseau, France, and colleagues have increased the fall time with a 鈥渜uantum trampoline鈥�.
Advertisement
In a microscopic chamber, they fired a specially designed laser pulse at the falling BECs. The pulse affected the BECs in the same way that a crystal lattice can affect light: since the atoms exhibit wave-like behaviour, they can be diffracted in a similar way to light in a crystal. By tuning the laser, the team were able to split up the wave, causing some of its components to bounce upwards. When the parts fell back down, the laser was pulsed so they split again, and so on. Eventually the parts recombined in an interference pattern. The device is less precise than existing atom interferometers, but the team plan to improve precision markedly ().