# Research

#### Overview

Our research group is focused on experiments designed to search for physics beyond the standard model using trapped ions.  For decades, the standard model (SM) of particle physics has provided the framework for our understanding of the universe [1].  It is one of the most stringently tested theories in all of physics, especially at high energies, and with the recent discovery of the Higgs boson, all known particles in the SM have been observed experimentally.  Despite the success of the SM, several major problems still remain unsolved (most notably, baryon asymmetry, the existence of dark matter and dark energy, and unification with gravity) [2]. With the advancement of precision measurements at the low-energy scale, the atomic, molecular, and optical (AMO) physics community is in a unique position to investigate the incomplete description of the universe provided by the SM.

To this end, our group is developing an experimental program to perform high precision laser spectroscopy of optical transitions in trapped highly charged ions (HCIs).  HCIs provide an exciting platform for developing new optical frequency standards that in some cases could be more immune to external perturbations than the current state-of-the art optical clocks [3–6] and, in other cases, could be more sensitive to time-variation of the fundamental constants (e. g. the fine-structure constant $$\alpha$$) [7].  We plan to combine techniques developed for quantum information processing and ion optical clocks with compact ion sources to create, trap, cool, and interrogate highly charged ions.  The goal of this program is to significantly increase the accuracy of HCI spectroscopy to improve the knowledge of the values of fundamental constants (e. g. $$\alpha$$ and/or the Rydberg constant $$R_{\infty}$$) and search for time-variation of these constants (e. g. $$\dot{\alpha}/ \alpha$$).  In this way, it will be possible to search for physics beyond the standard model including tests of the theory of relativity, quantum electrodynamics (QED), and investigations into the nature of dark matter.

References:
[1]  M. Tanabashi et al. (Particle Data Group), Phys. Rev. D 98, 030001 (2018).
[2]  M. S. Safronova, D. Budker, D. DeMille, Derek F. Jackson Kimball, A. Derevianko, and Charles W. Clark , Rev. Mod. Phys. 90, 025008 (2018).
[3]  T. L. Nicholson, S. L. Campbell, R. B. Hutson, G. E. Marti, B. J. Bloom, R. L. McNally, W. Zhang, M. D. Barrett, M. S. Safronova, G. F. Strouse, W .L. Tew, and J. Ye , Nature Communications 6, 6896 (2015).
[4]  N. Huntemann, C. Sanner, B. Lipphardt, Chr. Tamm, and E. Peik, Phys. Rev. Lett. 116, 063001 (2016).
[5]  W. F. McGrew, X. Zhang, R. J. Fasano, S. A. Schäffer, K. Beloy, D. Nicolodi, R. C. Brown, N. Hinkley, G. Milani, M. Schioppo, T. H. Yoon & A. D. Ludlow, Nature 564, 87–90 (2018).
[6]  S. M. Brewer, J.-S. Chen, A. M. Hankin, E. R. Clements, C. W. Chou, D. J. Wineland, D. B. Hume, and D. R. Leibrandt, Phys. Rev. Lett. 123, 033201  (2019).
[7]  M. G. Kozlov, M. S. Safronova, J. R. Crespo López-Urrutia, and P. O. Schmidt, Rev. Mod. Phys. 90, 045005 (2018).