Trapped bosons, thermodynamic limit and condensation: a study in the framework of resolvent algebras

Bose-Einstein condensation of atoms in a uniform potential

We have observed Bose-Einstein condensation of an atomic gas in the (quasi-)uniform three-dimensional potential of an optical box trap. Condensation is seen in the bimodal momentum distribution and the anisotropic time-of-flight expansion of the condensate. The critical temperature agrees with the theoretical prediction for a uniform Bose gas. The momentum distribution of our non-condensed quantum-degenerate gas is also clearly distinct from the conventional case of a harmonically trapped sample and close to the expected distribution in a uniform system. We confirm the coherence of our condens…

具有各向异性相互作用的囚禁原子凝聚体

Trapped atomic condensates with anisotropic interactions

研究了在电场诱导的偶极-偶极相互作用下囚禁原子凝聚体的基态性质。在阶梯近似的基础上，给出了一般非球形（极化）粒子各向异性相互作用赝势的严格构造方法。我们讨论有趣的功能，以前没有考虑目前可用的碱冷凝物。除了为控制原子与电场的相互作用提供定量评估外，我们的研究还可能为稀相互作用原子的玻色-爱因斯坦凝聚（BEC）的宏观相干性质提供新的线索。

Observation of local temporal correlations in trapped quantum gases

We measure the temporal pair correlation function $g^{(2)}(τ)$ of a trapped gas of bosons above and below the critical temperature for Bose-Einstein condensation. The measurement is performed {\it in situ} using a local, time-resolved single-atom sensitive probing technique. Third and fourth order correlation functions are also extracted. We develop a theoretical model and compare it with our experimental data, finding good quantitative agreement and highlighting the role of interactions. Our results promote temporal correlations as new observables to study the dynamics of ultracold quantum ga…

被淬火卷起：快速玻色-爱因斯坦凝聚尾流中的涡旋

Winding up by a quench: vortices in the wake of rapid Bose-Einstein condensation

由快速淬火引起的二级相变可以锁定密度远远超过其平衡期望值的拓扑缺陷。我们使用量子动力学理论表明，这种机制，最初假设在宇宙学的背景下，并分析到目前为止，只在平均场经典水平，应该允许自发产生的涡旋线被困玻色-爱因斯坦凝聚体的简单拓扑结构，或在环形凝聚体的绕组数。

Compositeness Effects in the Bose-Einstein Condensation

Small deviations from purely bosonic behavior of trapped atomic Bose-Einstein condensates are investigated with the help of the quon algebra, which interpolates between bosonic and fermionic statistics. A previously developed formalism is employed to obtain a generalized version of the Gross-Pitaeviskii equation. Two extreme situations are considered, the collapse of the condensate for attractive forces and the depletion of the amount of condensed atoms with repulsive forces. Experimental discrepancies observed in the parameters governing the collapse and the depletion of the condensates can b…

Thermodynamic measurement of the sound velocity of a Bose gas across the transition to Bose-Einstein condensation

We present an alternative method for determining the sound velocity in atomic Bose-Einstein condensates, based on thermodynamic global variables. The total number of trapped atoms was as a function of temperature carefully studied across the phase transition, at constant volume. It allowed us to evaluate the sound velocity resulting in consistent values from the quantum to classical regime, in good agreement with previous results found in literature. We also provide some insight about the dominant sound mode (thermal or superfluid) across a wide temperature range.