We have simulated the evaporative cooling of trapped atoms using a very efficient method originally introduced for the study of molecular gas dynamics. This straightforward and intuitive method allows the dynamics of the evaporative cooling process to be studied and requires fewer simplifications and assumptions than other methods. In particular, the method is not restricted to distributions close to equilibrium and therefore it can model accurately rapid forced evaporative cooling, which is an important technique for cooling trapped atoms. We present the results of simulations for forced evaporative cooling in one, two and three dimensions.We have simulated the evaporative cooling of trapped atoms using a very efficient method originally introduced for the study of molecular gas dynamics. This straightforward and intuitive method allows the dynamics of the evaporative cooling process to be studied and requires fewer simplifications and assumptions than other methods. In particular, the method is not restricted to distributions close to equilibrium and therefore it can model accurately rapid forced evaporative cooling, which is an important technique for cooling trapped atoms. We present the results of simulations for forced evaporative cooling in one, two and three dimensions.

European Quantum Electronics Conference (EQEC)Jan 1, 19963 citations

Dynamics of evaporative cooling for Bose-Einstein condensation

Huang Wu, E. Arimondo, Christopher J. Foot

We have simulated the evaporative cooling of a dilute gas of Bose particles including quantum statistics using a Monte Carlo method. This approach can model situations which are far away from quasiequilibrium such as occur during forced evaporative cooling. We have also simulated the dynamical formation of Bose-Einstein condensate for homogeneous and inhomogeneous Bose gases under the random-phase approximation. It was found that the rate of accumulation of Bose particles into low-energy states through collisions is increased by forced evaporation; and a macroscopic population at ground state can be reached at a time scale characterized by classical collision time for an inhomogeneous gas in a harmonic potential. We present the results of simulations for the evaporative cooling and formation of a Bose-Einstein condensate in one-, two-, and three-dimensional position cuts and energy cuts.We have simulated the evaporative cooling of a dilute gas of Bose particles including quantum statistics using a Monte Carlo method. This approach can model situations which are far away from quasiequilibrium such as occur during forced evaporative cooling. We have also simulated the dynamical formation of Bose-Einstein condensate for homogeneous and inhomogeneous Bose gases under the random-phase approximation. It was found that the rate of accumulation of Bose particles into low-energy states through collisions is increased by forced evaporation; and a macroscopic population at ground state can be reached at a time scale characterized by classical collision time for an inhomogeneous gas in a harmonic potential. We present the results of simulations for the evaporative cooling and formation of a Bose-Einstein condensate in one-, two-, and three-dimensional position cuts and energy cuts.

Physical Review AJul 1, 199767 citations

Quantum kinetic theory for evaporative cooling of trapped atoms: Growth of Bose-Einstein condensate

Makoto Yamashita, Masato Koashi, Nobuyuki Imoto

Evaporative cooling of trapped atoms is studied based on the quantum kinetic theory. We extend the classical analysis of Luiten et al. [Phys. Rev. A 53, 381 (1996)] to treat Bose statistics of alkali-metal atoms. Dynamics in evaporative cooling process is described by a kinetic equation for the truncated Bose-Einstein distribution function under the assumption that the system is close to the thermal equilibrium. This approach is applicable to the ``slow'' evaporative cooling normally adopted in most experiments for the efficient production of Bose-Einstein condensates. Time-evolution calculations explain the current experiment well with sodium atoms using a slow evaporative cooling and demonstrate a rapid growth of condensate in the cooling process.Evaporative cooling of trapped atoms is studied based on the quantum kinetic theory. We extend the classical analysis of Luiten et al. [Phys. Rev. A 53, 381 (1996)] to treat Bose statistics of alkali-metal atoms. Dynamics in evaporative cooling process is described by a kinetic equation for the truncated Bose-Einstein distribution function under the assumption that the system is close to the thermal equilibrium. This approach is applicable to the ``slow'' evaporative cooling normally adopted in most experiments for the efficient production of Bose-Einstein condensates. Time-evolution calculations explain the current experiment well with sodium atoms using a slow evaporative cooling and demonstrate a rapid growth of condensate in the cooling process.

Physical Review AMar 1, 199925 citations

Optimization of evaporative cooling

Charles A. Sackett, C. C. Bradley, Randall G. Hulet

Recent experiments have used forced evaporative cooling to produce Bose-Einstein condensation in dilute gases. The evaporative cooling process can be optimized to provide the maximum phase-space density with a specified number of atoms remaining. We show that this global optimization is approximately achieved by locally optimizing the cooling efficiency at each instant. We discuss how this method can be implemented, and present the results for our $^{7}\mathrm{Li}$ trap. The predicted behavior of the gas is found to agree well with experiment.Recent experiments have used forced evaporative cooling to produce Bose-Einstein condensation in dilute gases. The evaporative cooling process can be optimized to provide the maximum phase-space density with a specified number of atoms remaining. We show that this global optimization is approximately achieved by locally optimizing the cooling efficiency at each instant. We discuss how this method can be implemented, and present the results for our $^{7}\mathrm{Li}$ trap. The predicted behavior of the gas is found to agree well with experiment.

Physical Review AMay 1, 199739 citations

Simulation Method for Evaporative Cooling of Trapped Bose Gases at Finite Temperatures

Emiko Arahata, Tetsuro Nikuni

Abstract We have devised a simulation method for studying the evaporative cooling process of trapped Bose-Einstein condensates at finite temperatures, leveraging the Zaremba-Nikuni-Griffin (ZNG) formalism. This framework incorporates the generalized Gross-Pitaevskii (GP) equation and a semiclassical kinetic equation governing the behavior of the thermal cloud. Our approach builds upon the numerical techniques pioneered by Jackson and Zaremba, which involve simulating the kinetic equation using test particles. A pivotal aspect of our method lies in emulating the evaporative cooling process by selectively removing test particles with high energy. Through extensive simulations, we demonstrate the efficacy of our approach in accurately describing condensate growth during evaporative cooling. Furthermore, we extend our simulations to investigate the formation of vortex lattices during evaporative cooling in the presence of a rotating thermal cloud. This comprehensive analysis provides valuable insights into the intricate dynamics of trapped Bose-Einstein condensates undergoing evaporative cooling processes.Abstract We have devised a simulation method for studying the evaporative cooling process of trapped Bose-Einstein condensates at finite temperatures, leveraging the Zaremba-Nikuni-Griffin (ZNG) formalism. This framework incorporates the generalized Gross-Pitaevskii (GP) equation and a semiclassical kinetic equation governing the behavior of the thermal cloud. Our approach builds upon the numerical techniques pioneered by Jackson and Zaremba, which involve simulating the kinetic equation using test particles. A pivotal aspect of our method lies in emulating the evaporative cooling process by selectively removing test particles with high energy. Through extensive simulations, we demonstrate the efficacy of our approach in accurately describing condensate growth during evaporative cooling. Furthermore, we extend our simulations to investigate the formation of vortex lattices during evaporative cooling in the presence of a rotating thermal cloud. This comprehensive analysis provides valuable insights into the intricate dynamics of trapped Bose-Einstein condensates undergoing evaporative cooling processes.

arXiv:2310.03250Springer proceedings in physicsJan 1, 20260 citations

Dynamic equation for evaporative cooling of trapped atoms in microgravity

Xiaolong Yuan, Jiachen Yu, H. Li +4 more

In this paper, to investigate how atoms evaporate and cool in microgravity environments of the space station, we have developed the dynamic equation for evaporative cooling of trapped atoms and obtained the analytical expression of atomic temperature with respect to trapping laser parameters and gravitational acceleration. In our model, the evaporation of atoms is equivalent to applying a damping force to the trapped atoms, and the evaporative cooling process of trapped atoms is comprehended as the damped oscillation of trapped atoms in the optical dipole traps. By introducing the gravity in our model, we obtained the analytical model of temperature variation with gravity after cooling, and the theoretical results agree well with the evaporation experiment of rubidium-87 atoms on the ground. Our theoretical results show that, compared with the atomic evaporative cooling experiment on the ground, the microgravity environment of the space station can achieve cooler atomic gases when the losses of atoms, such as the one-body loss caused by background-gas collisions and the three-body recombination loss caused by interatomic inelastic collisions, can be ignored.In this paper, to investigate how atoms evaporate and cool in microgravity environments of the space station, we have developed the dynamic equation for evaporative cooling of trapped atoms and obtained the analytical expression of atomic temperature with respect to trapping laser parameters and gravitational acceleration. In our model, the evaporation of atoms is equivalent to applying a damping force to the trapped atoms, and the evaporative cooling process of trapped atoms is comprehended as the damped oscillation of trapped atoms in the optical dipole traps. By introducing the gravity in our model, we obtained the analytical model of temperature variation with gravity after cooling, and the theoretical results agree well with the evaporation experiment of rubidium-87 atoms on the ground. Our theoretical results show that, compared with the atomic evaporative cooling experiment on the ground, the microgravity environment of the space station can achieve cooler atomic gases when the losses of atoms, such as the one-body loss caused by background-gas collisions and the three-body recombination loss caused by interatomic inelastic collisions, can be ignored.

Physical Review AApr 16, 20242 citations

^{7}\mathrm{Li}

trap. The predicted behavior of the gas is found to agree well with experiment.