Ultracold strontium is well-known for its use in highly accurate optical lattice clocks [1-4]. However, in recent years the high measurement precision afforded by strontium has led to a new class of experiments, which use the techniques of atomic clocks to realize novel many-body states [5] and exotic quantum effects [6,7].

Although ultracold strontium is capable of extraordinary measurement precision [8], it lacks the long-range interactions that are the foundation of many exciting new experiments [9-12]. Fortunately atoms can be endowed with strong, long-range interactions by coupling them to Rydberg states [13]. The Rydberg interaction has been used in neutral atoms to demonstrate entanglement [14], quantum gates [13], and interesting many-body effects like Rydberg spatial ordering and Ising crystallization [15,16].

The aim of this project is to combine the precision of atomic clocks with long-range interactions using Rydberg states. This experiment is based on a low-entropy gas of strontium confined in a 2D lattice potential and dressed by a Rydberg state. Rydberg dressing allows the interaction strength to be tunable [17], and the system is also designed with the ability to address lattice sites independently. These ingredients result in an apparatus that can precisely control the quantum states and interaction strength of every atom.

Such a high degree of control could enable numerous applications, but we primarily focus on quantum information and quantum simulation.

References:

[1] T.L. Nicholson, et al. “Systematic evaluation of an atomic clock at 2e-18 total uncertainty.” *Nature Communications* **6**, 6896 (2015).

[2] I. Ushijima, et al. “Cryogenic optical lattice clocks.” *Nature Photonics ***9**, 185 (2015).

[3] R. Le Targat, et al. “Experimental realization of an optical second with strontium lattice clocks.” *Nature Communications ***4**, 2109 (2013).

[4] S. Falke, et al. “A strontium lattice clock with 3e-17 inaccuracy and its frequency.” *New Journal of Physics ***16**, 073023 (2014).

[5] M.J. Martin, et al. “A quantum many-body spin system in an optical lattice clock.” *Science* **341**, 632 (2013).

[6] X. Zhang, et al. “Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism.” *Science* **345**, 1467 (2014).

[7] S. Kolkowitz, et al. “Spin-orbit-coupled fermions in an optical lattice clock.” *Nature* **542**, 66 (2017).

[8] S.L. Campbell, et al. “A Fermi-degenerate three-dimensional optical lattice clock.” *Science* **358**, 90 (2017)

[9] K. Aikawa, et al. “Observation of Fermi surface deformation in a dipolar quantum gas.” *Science* **345**, 1484 (2014).

[10] Y. Tang, et al. “Anisotropic expansion of a thermal dipolar Bose gas.” *Physical Review Letters* **117**, 155301 (2016).

[11] J.P. Covey, et al. “Doublon dynamics and polar molecule production in an optical lattice.”* Nature Communications* **7**, 11279 (2016).

[12] J.W. Park, et al. “Second-scale nuclear spin coherence time of ultracold 23Na40K molecules.” *Science* **357**, 372 (2017).

[13] M. Saffman, T.G. Walker, and K. Molmer. “Quantum information with Rydberg atoms.” *Reviews of Modern Physics* **82**, 2313 (2010).

[14] T. Wilk, et al. “Entanglement of two individual neutral atoms using Rydberg blockade.” *Physical Review Letters* **104**, 010502 (2010).

[15] P. Schauss, et al. “Observation of spatially ordered structures in a two-dimensional Rydberg gas.” *Nature* **491**, 87 (2012).

[16] P. Schauss, et al. “Crystallization in Ising quantum magnets.” *Science* **347**, 1455 (2015).

[17] J. Zeiher, et al. “Many-body interferometry of a Rydberg-dressed spin lattice.” *Nature Physics* **12**, 1095 (2016).