Bouncing atoms take a measure of gravity
Pretty cool. The experiment uses a technique used in interferometry, where a laser standing wave induces an absorption-emission cycle of an atom, so it receives a momentum “kick” of twice the photon momentum (one kick for absorption, and once for emission), effectively making a diffraction grating out of light if they were moving through the standing wave, and uses this to bounce the falling atoms.
If the colour of the laser light and the frequency of pulses are set correctly, the atoms will be set bouncing and the acceleration due to gravity can be deduced from the experimental parameters and Planck’s constant. The team managed to sustain this bouncing for about 100 cycles, which they say is the equivalent of dropping the atoms about 2 cm in a standard experiment.
Inflated claims of wonderfulness would have been more credible if the experimental value of gee did not imply the lab was resting upon a hugely thick lead slab.