Single-shot reconstruction of the density profile of a dense atomic gas

Fast and efficient preparation of 1D chains and dense cold atomic clouds

We report the efficient and fast ($\sim 2\mathrm{Hz}$) preparation of randomly loaded 1D chains of individual $^{87}$Rb atoms and of dense atomic clouds trapped in optical tweezers using a new experimental platform. This platform is designed for the study of both structured and disordered atomic systems in free space. It is composed of two high-resolution optical systems perpendicular to each other, enhancing observation and manipulation capabilities. The setup includes a dynamically controllable telescope, which we use to vary the tweezer beam waist. A D1 $Λ$-enhanced gray molasses enhances t…

Topological properties of a dense atomic lattice gas

We investigate the existence of topological phases in a dense two-dimensional atomic lattice gas. The coupling of the atoms to the radiation field gives rise to dissipation and a non-trivial coherent long-range exchange interaction whose form goes beyond a simple power-law. The far-field terms of the potential -- which are particularly relevant for atomic separations comparable to the atomic transition wavelength -- can give rise to energy spectra with one-sided divergences in the Brillouin zone. The long-ranged character of the interactions has another important consequence: it can break of t…

Storage and release of subradiant excitations in a dense atomic cloud

We report the observation of subradiance in dense ensembles of cold $^{87}$Rb atoms operating near Dicke's regime of a large number of atoms in a volume with dimensions smaller than the transition wavelength. We validate that the atom number is the only cooperativity parameter governing subradiance. We probe the dynamics in the many-body regime and support the picture that multiply-excited subradiant states are built as a superposition of singly-excited states that decay independently. Moreover, we implement an experimental procedure to release the excitation stored in the long-lived modes in …

Light scattering from dense cold atomic media

We theoretically study the propagation of light through a cold atomic medium, where the effects of motion, laser intensity, atomic density, and polarization can all modify the properties of the scattered light. We present two different microscopic models: the "coherent dipole model" and the "random walk model", both suitable for modeling recent experimental work done in large atomic arrays in the low light intensity regime. We use them to compute relevant observables such as the linewidth, peak intensity and line center of the emitted light. We further develop generalized models that explicitl…

稠密光阱原子系综动力学退耦的过程层析

Process tomography of dynamical decoupling in a dense optically trapped atomic ensemble

原子系综在量子信息科学中有许多潜在的应用。由于集体增强，在高密度下使用系综增加了量子操作的整体效率，但同时也增加了碰撞率并导致更快的退相干。在这里，我们报告的实验与光学捕获的87 Rb原子演示了20倍的相干时间增加时，应用动态去耦序列与超过200 π脉冲。我们进行量子过程层析成像，并表明，使用去耦方案的光学深度为230的密集系综可以用作原子存储器的相干时间超过3秒。

用超冷原子玻色子-费米子混合物模拟致密QCD物质

Simulating dense QCD matter with ultracold atomic boson-fermion mixtures

我们描绘，作为一个模拟的两味稠密夸克物质，相结构的多体混合物的原子玻色子和费米子在两个内部状态的可调玻色子费米子吸引力。玻色子b对应于双夸克，费米子f对应于未成对夸克。对于弱的b-f吸引，系统是玻色-爱因斯坦凝聚体和简并费米子的混合体，而对于强吸引，形成复合b-f费米子N，类似于核子，由于自旋单态通道中的N-N吸引，它们是超流的。我们确定了有限温度下的对称性破缺模式作为b-f耦合强度的函数，并将相图与致密QCD的相图联系起来。

Near-resonant light transmission in two-dimensional dense cold atomic media with short-range positional correlations

Light propagation in disordered media is a fundamental and important problem in optics and photonics. In particular, engineering light-matter interaction in disordered cold atomic ensembles is one of the central topics in modern quantum and atomic optics. The collective response of dense atomic gases under light excitation, which crucially depends on the spatial distribution of atoms and the geometry of the ensemble, has important impacts on quantum technologies like quantum sensors, atomic clocks and quantum information storage. Here we analyze near-resonant light transmission in two-dimensio…

包含磁偶极相互作用的稠密冷原子气体中的协同效应

Cooperative effects in dense cold atomic gases including magnetic dipole interactions

本文理论研究兼具电、磁偶极相互作用的冷原子气体，分别用多体物理和开放系统方法分析量子简并与非简并情形，揭示自旋模型、光散射方向性及亚/超辐射与量子统计的关系。

干涉玻色凝聚原子云的相位估计

Phase Estimation With Interfering Bose-Condensed Atomic Clouds

本文研究了如何从原子位置测量中估计从双势阱中释放的两个玻色-爱因斯坦凝聚体的相对相位。我们表明，相位估计灵敏度通过拟合的平均密度的干涉图案是从根本上有界的散粒噪声。通过从$\sqrt N$（或更高）关联函数的测量来估计相位，可以克服该界限。最佳估计策略需要测量$N$阶关联函数。我们还证明了第二种估计方法-基于干涉图样的质量质心的检测-提供子散粒噪声灵敏度。然而，这两个协议的实施可能在实验上具有挑战性。