Atom–light interactions govern the coherent and dissipative dynamics of atomic systems, with profound implications for experimental platforms such as optical lattice clocks and tweezer arrays. I will discuss two regimes where geometry and atomic spacing shape the interaction-induced collective effects. In the far-field regime, spatially separated atoms emit into many photonic modes and undergo position-dependent frequency shifts. Motivated by a recent experiment [1], I will explore whether such extended atomic ensembles can undergo a superradiant phase transition [2]—typically associated with a tightly-confined ensemble [3], such as in cavity-qed setups [4]. In the near-field regime, I will discuss how weakly driven atoms can depart from a classical description when more than two internal levels of an atom are involved, generating strong quantum correlations in the long-lived ground subspace [5]. I will propose a subwavelength-spaced array using a cyclic transition in 88Sr to test these predictions.

[1] G. Ferioli, A. Glicenstein, I. Ferrier-Barbut, and A. Browaeys, A non-equilibrium superradiant phase transition in free space, Nature Physics 19, 1345 (2023).

[2] S. Agarwal, E. Chaparro, D. Barberena, A. P. Orioli, G. Ferioli, S. Pancaldi, I. Ferrier-Barbut, A. Browaeys, and A. Rey, PRX Quantum 5, 040335 (2024).

[3] P. D. Drummond and H. J. Carmichael, Optics Communications 27, 160 (1978).

[4] E. Y. Song, D. Barberena, D. J. Young, E. Chaparro, A. Chu, S. Agarwal, Z. Niu, J. T. Young, A. M. Rey, and J. K. Thompson, Science Advances 11, eadu5799 (2025).

[5] S. Agarwal, A. P. Orioli, J. K. Thompson, and A. M. Rey, Phys. Rev. Lett. 133, 233003 (2024).