Resolving the gravitational redshift across a millimetrescale atomic sample
Abstract
Einstein's theory of general relativity states that clocks at different gravitational potentials tick at different rates relative to lab coordinates—an effect known as the gravitational redshift^{1}. As fundamental probes of space and time, atomic clocks have long served to test this prediction at distance scales from 30 centimetres to thousands of kilometres^{24}. Ultimately, clocks will enable the study of the union of general relativity and quantum mechanics once they become sensitive to the finite wavefunction of quantum objects oscillating in curved spacetime. Towards this regime, we measure a linear frequency gradient consistent with the gravitational redshift within a single millimetrescale sample of ultracold strontium. Our result is enabled by improving the fractional frequency measurement uncertainty by more than a factor of 10, now reaching 7.6 × 10^{−21}. This heralds a new regime of clock operation necessitating intrasample corrections for gravitational perturbations.
 Publication:

Nature
 Pub Date:
 February 2022
 DOI:
 10.1038/s41586021043497
 arXiv:
 arXiv:2109.12238
 Bibcode:
 2022Natur.602..420B
 Keywords:

 Physics  Atomic Physics;
 Physics  Instrumentation and Detectors;
 Quantum Physics
 EPrint:
 27 pages, 4 figures, 1 table