Today Xin, Jack, Brett, and Haoran achieved a major milestone in the development of a multiplexed optical lattice clock and its use for new tests of relativity. The animated GIF below shows strontium atoms in an “atomic elevator” made of light, rising with respect to gravity (which is pointing down in this image) at a rate of ~3 mm/second.

The second image below, also taken today shows the preparation and simultaneous imaging of two ensembles of strontium atoms in our vacuum chamber, spatially separated by ~1 mm, a critical component of our new “multiplexed optical lattice clock” design.

This is a major step towards measuring the “gravitational redshift” due to earth’s gravity at a new length scale. In a gravitational field such as Earth’s, a clock that is elevated with respect to gravity will tick faster than a lower clock. This effect of general relativity is called the gravitational redshift, and it has previously been observed at the ~30 cm scale, but has not yet been observed at the cm or mm scale.

As shown in A in the diagram below, the Einstein equivalence principle, a foundational tenet of the theory of relativity, states that an observer cannot distinguish between being inside an elevator on the surface of earth and experiencing an acceleration due to gravity g (panel I), and being in an elevator accelerating through space with an acceleration a=g (panel II). As shown in B, by combining our multiplexed optical lattice clock with the ability to accelerate atoms as in the “atomic elevator” shown above, we will be able perform a novel and direct test of the Einstein equivalence principle in our lab.

Congratulations to Matt, Aedan, and Sam, whose paper “State-dependent phonon-limited spin relaxation of nitrogen-vacancy centers” has now been posted to the arXiv!

Xin, Jack, Haoran, and Brett have successfully trapped strontium atoms in an optical lattice for the first time! (The first time in our lab, this is already a very well established technique in experimental atomic physics.) The strontium atoms are held in a standing wave of light formed by two counter-propagating laser beams, which forms a simple one-dimensional crystal of light. Below is a picture taken with a CCD camera of the shadow cast by these atoms on a laser beam.

This is a major milestone on the way to building a working optical lattice atomic clock.

Congratulations to Aedan and Matt, whose paper “Fast relaxation on qutrit transitions of nitrogen-vacancy centers in nanodiamonds” has now been published online in Physical Review Applied! For those who don’t have access to the journal, a pre-print can be found on the arXiv here: https://arxiv.org/abs/1910.10813.

And if you prefer to get your physics fix in doses of 140 characters or less, here’s a tweet from the department communications director Sarah Perdue summarizing our paper (based off a much longer synopsis provided by Shimon):