利用原子阵列中的亚辐射和“选择辐射”指数改进光子存储性能
Exponential improvement in photon storage fidelities using subradiance and "selective radiance" in atomic arrays
摘要：
量子光学的核心目标是实现光子和原子之间的有效相互作用。在几乎所有基于这种系统的应用中，一个基本的限制来自于自发发射，其中光子被原子吸收，然后重新散射到不需要的通道中。在原子系综的典型处理中，假设这种再散射独立地发生，并且以单个孤立原子给出的速率发生，这进而在诸如量子存储器或量子门之类的应用中产生保真度的标准极限。然而，这个假设可能会被违反。特别地，集体原子激发的自发发射可以通过发射中的强干扰而被显著抑制。到目前为止，亚辐射现象的物理基础和利用它的技术还没有得到很好的理解。在这项工作中，我们提供了一个全面的处理这个问题。首先，我们表明，在有序的原子阵列在自由空间中，subradiant状态获得的光学模式，由阵列引导，只发射由于从有限链的末端散射的解释。我们还阐明了在多激发极限下的次辐射态的性质。最后，我们介绍了选择性辐射的新概念。尽管次辐射态经历到所有光学模式的耦合减少，但是选择性辐射态被定制为同时有效地辐射到期望的通道中，同时抑制散射到不期望的通道中，从而实现增强的原子-光界面。我们表明，这些国家自然出现在原子链耦合到纳米光子结构，我们分析了利用这些国家的光子存储的性能。我们发现，选择性辐射状态允许光子存储误差，指数级更好地与原子数比以前已知的界限。
英文摘要：
A central goal within quantum optics is to realize efficient interactions between photons and atoms. A fundamental limit in nearly all applications based on such systems arises from spontaneous emission, in which photons are absorbed by atoms and then re-scattered into undesired channels. In typical treatments of atomic ensembles, it is assumed that this re-scattering occurs independently, and at a rate given by a single isolated atom, which in turn gives rise to standard limits of fidelity in applications such as quantum memories or quantum gates. However, this assumption can be violated. In particular, spontaneous emission of a collective atomic excitation can be significantly suppressed through strong interference in emission. Thus far the physics underlying the phenomenon of subradiance and techniques to exploit it have not been well-understood. In this work, we provide a comprehensive treatment of this problem. First, we show that in ordered atomic arrays in free space, subradiant states acquire an interpretation in terms of optical modes that are guided by the array, which only emit due to scattering from the ends of the finite chain. We also elucidate the properties of subradiant states in the many-excitation limit. Finally, we introduce the new concept of selective radiance. Whereas subradiant states experience a reduced coupling to all optical modes, selectively radiant states are tailored to simultaneously radiate efficiently into a desired channel while scattering into undesired channels is suppressed, thus enabling an enhanced atom-light interface. We show that these states naturally appear in chains of atoms coupled to nanophotonic structures, and we analyze the performance of photon storage exploiting such states. We find that selectively radiant states allow for a photon storage error that scales exponentially better with number of atoms than previously known bounds.
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