Trapped atoms, suspended aloft on a lattice of laser light for as long as 20 seconds, allow for highly sensitive measurements of gravity, according to a new study published today (November 8, 2019) in the journal Science, which describes a new approach to atom interferometers.
The new design greatly enhances the sensitivity and precision of gravitational measurements over previous iterations and could be used in tests of general relativity or other investigations into fundamental physics.
Atom interferometry is a powerful technique that uses the quantum properties of exceedingly cold atoms to precisely measure various aspects of physics, such as inertia or gravity, or to search for new physical or atomic phenomena. Like Galileo’s infamous experiment at the Leaning Tower of Pisa, gravimeters based on atom interferometry can detect slight variations in gravitational fields by observing the behavior of ‘dropped’ atoms. However, the sensitivity and precision of gravitational measurements are largely dependent on the length of time a freely falling atom can be interrogated and the distance it falls, which until now has been limited to only 2.3 seconds in a span of 10 meters (33 feet).
Rather than dropping atoms like balls from a tower, Victoria Xu and colleagues describe a trapped atom interferometer capable of expanding the interrogation time to 20 seconds.
Xu et al. use an optical lattice to control and suspend ultracold atoms in place, greatly increasing the ability to measure their behavior in a gravitational field and, by extension, the precision of the gravitational measurements. What’s more, the results show a more than 10,000-fold suppression in the vibrational noise common to even the most state-of-the-art atomic gravimeters, drastically improving the signal-to-noise ratio of measurements. The authors show that the new design allows for highly sensitive and precise yet compact atomic setups.
Reference: “Probing gravity by holding atoms for 20 seconds” by Victoria Xu, Matt Jaffe, Cristian D. Panda, Sofus L. Kristensen, Logan W. Clark and Holger Müller, 8 November 2019, Science.