Testing relativity on a tabletop with optical lattice atomic clocks

The remarkable precision of optical atomic clocks offers sensitivity to new and exotic physics through tests of relativity, searches for dark matter, gravitational wave detection, and probes for beyond Standard Model particles. While much of optical clock research has focused on improving their absolute accuracy, many searches for new physics can be performed with relative comparisons between clocks. To this end, we have realized a “multiplexed” strontium optical lattice clock consisting of two or more clocks in one vacuum chamber, forming a miniature clock network. This enables us to bypass the primary limitations to typical atomic clock comparisons and to achieve new levels of precision, enabling us to perform novel tests of relativity in the lab.

In this talk I will explain the motivation, concept, and operating principles of our multiplexed optical lattice clock. I will then present experimental results in which we performed a novel, blinded, precision test of the gravitational redshift with a vertical array of 5 evenly-spaced ensembles of ultra-cold strontium atoms spanning a total height difference of 1 cm. I will present the error budget produced from our systematic evaluation, and the unblinded results of our first test. I will explain how these results can also be viewed as proof-of-principle measurements of relativistic gravitational potential differences at the millimeter scale, with applications to geodesy. I will introduce recent experimental results demonstrating how we can use our apparatus to study and leverage the level structure of strontium in order to extend the achievable coherent clock interrogation times. Finally, I will discuss the outlook for performing future searches for new physics using this apparatus, as well as a second-generation apparatus currently under construction, including a novel direct test of the Einstein Equivalence Principle, and explorations of the interplay between general relativity and quantum mechanics.