13ª Semana Integrada do Instituto de Física de São Carlos

CoupledDipoles.jl: A Julia package for cold atoms

21 de ago. de 2023 10:30

1h 30m

Salão de Eventos USP

Normal 10h30 - 12h00

Descrição

In recent years, there has been a growing interest in studying collective effects, such as sub- and superradiance, especially with cold atom experiments. These experiments typically involve a large number of atoms, and their theoretical description has often focused on capturing the effective dynamics rather than the full quantum description of the system. The Linear Optics regime, which also corresponds to the Single-Excitation regime, has been extensively used through the so-called Coupled Dipole Equations, provided reasonably accurate results for several weak-drive experiments. However, as experiments explore increasingly complex regimes (strong drive, with many excitations), the demand for more sophisticated theoretical models has increased. (1) Our objective is to establish systematic comparisons between the already-established and newly-derived models, with an emphasis on their efficient implementation through numerical codes. To this end, we developed a library that serves as a foundation for present and future simulations, called CoupledDipoles.jl, written in the language Julia. This library was designed to deliver an efficient implementation of the basic routines for our cold atom system at different levels of modeling. It relies, for example, on the multi-threading paradigm of the parts of the code that benefit most from parallel programming, based on a study of the most common scenarios of simulations. Moreover, its code structure is also designed to be easily adaptable to explore other regimes and levels of modeling.We apply our tools to the study of Anderson Localization, exploring how the statistics of the scattered light may reveal experimental signatures of the localization transition. (2) While the previous results were based on the single-excitation approach, we investigated these statistics using our numerical tools, using the non-linear set of equations (Mean Field Equations) which takes into account the excited population of the atoms and thus describes the moderate-drive regime. This has allowed us to demonstrate that the presence of multiple excitations in the system will not prevent the localization phenomenon, provided that one monitors the elastically scattered light.Currently, various numerical results are scattered across different research groups, with the technical implementation often not provided, which can be considered a weakness from a scientific point of view. The ultimate goal of this package is to stimulate more unified behavior in the community, providing the first step of an adaptable package. By providing a centralized resource, we aim to facilitate collaboration across groups, and stimulate new work and the exploration of new regimes in the field.

Referências

1 CIPRIS, A. et al. Subradiance with saturated atoms: population enhancement of the long-lived states. Physical Review Letters, v. 126, n. 10, p. 103604-1-103604-6, Mar. 2021.

2 COTTIER, F. et al. Microscopic and macroscopic signatures of 3D Anderson localization of light. Physical Review Letters, v. 123, n. 8, p. 083401-1-083401-6, Aug. 2019.