Collective Atom Interaction with Photons

与我们通常所熟悉的较大物体相比，小而冷的物体的行为方式令人难以置信地奇怪。当许多对象相互作用时，这种奇怪的行为会变得更加复杂。最近我们在控制小物体方面的进展带来了量子计算机和量子模拟器的前景，这可能会导致我们的计算能力取得惊人的进步。在欧洲、亚洲和美洲进行的这类研究，正在使我们所控制的系统的复杂性迅速提高。该项目将使用理论和计算方法来研究多个原子之间的相互作用，这已被提议作为量子计算和量子模拟的平台。特别是，这个小组将集中在原子被定位成规则阵列的情况下。世界上有许多小组已经证明了将原子固定在重复正方形的角落上的能力，这个小组将调查现实情况，以预测和理解它们的集体进化。这些系统很难理解，因为一个原子的变化会影响第二个原子的变化，第二个原子的变化又会影响第三个原子的变化，但它们的研究非常值得，因为它会产生丰富的结果，这些结果本质上是有趣的，也可能成为量子传感器、计算机或模拟器的基础。这些研究的一个关键特征是发展理论和计算技术，以涵盖光-原子相互作用的所有方面，包括原子的反冲、光子的偏振和多体相干性。该项目的重点是原子与光的集体相互作用，其中许多原子的存在改变了它们单独与光子相互作用的方式。该小组将主要处理晶格间距小于波长的原子阵列。在这种情况下，原子间的延迟偶极-偶极相互作用导致了光子-原子的集体相互作用：这种相互作用与光子与单个原子的相互作用性质不同。在一组项目中，该小组将探索单光子与原子阵列相互作用导致动量和能量转移到原子质心运动的效果。这将在两个层次上进行研究：假设突然相互作用的近似和更准确的治疗，包括质量中心的量化运动。该小组将研究几种情况，包括特定的集体状态如何导致阵列中特定原子的反冲，以及阵列对如何用于纠缠遥远的量子比特和研究基础光学力学研究。这种腔结构可能导致特别大的质心反冲，这将影响它们的应用，也可能导致有趣的基础物理。另一组项目将研究几个光子如何与原子阵列相互作用。新的现象是预期的，因为当一个光子入射到阵列上时，阵列中的任何原子都可以被激发，但是，随着更多的光子，已经被激发的原子不能吸收第二个光子。与单光子情形相比，这种约束导致了原子阵列中不同的关联和纠缠。纠缠的一种可能性是在不同原子的空间波函数中，因为光子反冲将取决于阵列中原子的激发的存在。该小组还将研究光子中的相关性;相关性可能发生在光子在超辐射过程中通过相关自发衰变发射时，也可能发生在阵列成对或多对发射光子时。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Small, cold objects behave in ways that are incredibly bizarre compared to larger, familiar objects of our normal experience. This strange behavior can become more emphatic when many objects interact with each other. Recent advances in our control of small objects have led to prospects of quantum computers and quantum simulators, which could lead to astounding advances in our computational abilities. Studies of this type in Europe, Asia, and the Americas are leading to rapid advances in the complexity of systems under our control. This project will use theoretical and computational methods to study the interaction between many atoms using light, which has been proposed as a platform for quantum computation and quantum simulation. In particular, this group will focus on cases where the atoms are position into a regular array. There are many groups around the world that have demonstrated the ability to hold the atoms, for example, on the corners of a repeating square and this group will investigate realistic situations to predict and understand their collective evolution. These systems are hard to understand because changes to one atom affect those on a second atom, which affect those on a third atom …, but their study is eminently worthwhile because it leads to a richness in outcome which is intrinsically interesting and might also serve as the basis of quantum sensors, computers, or simulators. A key feature of these studies will be the development of theoretical and computational techniques to include all aspects of light-atom interactions, including the recoil of atoms, the polarization of the photon, and many-body coherences.The focus of this project is the collective interaction of atoms with light where the presence of many atoms changes how they individually interact with the photons. The group will mainly treat atom arrays where the lattice spacing is smaller than the wavelength. For this condition, the retarded dipole-dipole interaction between atoms leads to collective photon-atom interaction: the interaction is qualitatively different from that of a photon with a single atom. In one group of projects, the group will explore the effect where single photons interacting with an array of atoms leads to momentum and energy transferred to the atoms' center-of-mass motion. This will be investigated at two levels: the approximation where a sudden interaction is assumed and a more accurate treatment including the center of mass quantized motion. The group will investigate several cases, including how specific collective states lead to kicks for particular atoms in the array and how array pairs could be used to entangle distant qubits and to study fundamental optomechanical studies. The cavity configuration could lead to especially large center-of-mass recoil, which would affect their applications and could lead to interesting fundamental physics as well. The other group of projects will study how several photons interact with the atom array. New phenomena are expected because when one photon is incident on the array, any atom in the array can be excited, but, with more photons, already excited atoms cannot absorb a second photon. This constraint leads to different correlations and entanglement in the atom array compared to the one photon cases. One possibility for entanglement is in the spatial wave function of the different atoms because the photon recoil will depend on the presence of excitations of atoms in the array. The group will also study correlation in the photons; correlation can occur when photons are emitted through correlated spontaneous decay during superradiance or could occur when the array transmits photons in pairs or more.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.