Quantum Plasmonics for Low-Photon-Number Nonlinear Optics and Quantum Circuits

标题：用于低光子数非线性光学和量子电路的量子等离子体金属纳米结构可以表面等离子体极化的形式将光限制在纳米尺度内，表面等离子体极化是在金属和介质表面之间传播的电磁波。表面等离子体可以将光学设备微型化到纳米级，还可以产生极高的电磁强度，从而产生强烈的光-物质相互作用。这些特性为超紧凑型有源光学器件，如光开关、调制器和波长转换器，提供了以非常高的速度和低能量运行的可能性。然而，要实现这些能力，需要具有强烈非线性光学响应的等离子体纳米结构。最近的理论工作表明，当表面等离子体与单个量子发射体相互作用时，两个系统可以杂交形成新的光和物质的耦合模式。在这种混合模式下，单个等离子体激元可以产生非线性光学响应，为非线性等离子体电路在基本量子能量极限下工作铺平了道路。然而，到目前为止，这种混合机制仍然难以捉摸，因为量子发射体通常会因为声子和光谱漂移而遭受巨大的退相。在这个项目中，我们将研究金属纳米结构与砷化铟量子点之间的相互作用，以研究杂化区域，并开发超快非线性和量子器件。砷化铟量子点表现出光谱上的纯发射，这使它们成为实现杂交的理想材料。我们将使用这些高质量的量子发射体来演示杂交，并探索其非线性和量子光学性质。该计划最终可能为具有超低能量耗散的纳米级光子设备以及提供指数计算加速和无条件安全通信的紧凑量子电路铺平道路。该计划还将支持一项为本科生和高中生提供研究机会的推广工作。等离子体纳米结构可以通过将光以表面等离子体激元(或简称等离子体)的形式限制在纳米级，从而极大地增强光与物质的相互作用。最近，有理论预测，当量子发射体被放置在等离子体纳米结构的高场区域时，两个系统可以杂化。在这种混合模式下，发射体和等离子体激元形成新的耦合模式，同时具有原子和光子性质。这些混合模式在单光子水平附近表现出很强的光学非线性，使其成为开发超低功耗光电和量子器件的极具吸引力的系统。由于声子散射和光谱漂移，量子发射体通常表现出快速的偶极子退相，因此单量子发射体和等离子体之间的杂交还没有被证实。这种退相破坏了产生混合模式的量子干涉。我们建议使用砷化铟(InAs)量子点来克服这个问题，这种量子点表现出窄的和几乎转换有限的光发射，使它们成为获得杂化区域的有前途的系统。将这些InAs量子点与金属纳米结构偶联的一个关键挑战是，它们嵌入在砷化镓基质中，不容易沉积到等离子体设备上。我们将通过结合器件设计和最先进的纳米制造技术来应对这一挑战。我们将描述制作的器件的线性和非线性特性。然后，我们将利用这种混合机制来演示一种纳米光子光学晶体管，其中一个被吸收的控制光子可以切换许多信号光子。我们还将利用混合机制在量子点中的单个捕获自旋和表面等离子激元之间创建界面，这可以作为纳米级量子电路的基本构建块。这一计划最终可能为具有超低能量耗散的纳米级非线性光子器件和提供指数计算加速和无条件安全通信的紧凑量子电路铺平道路。

Title: Quantum Plasmonics for Low-Photon-Number Nonlinear Optics and Quantum CircuitsMetallic nanostructures can confine light to nanometer length scales in the form of surface-plasmon polaritons, which are electromagnetic waves that propagate at the interface between metallic and dielectric surfaces. Surface plasmons can miniaturize optical devices to the nanoscale, and also generate extremely high electromagnetic intensities that create strong light-matter interactions. These properties open up the possibility for ultra-compact active optical devices such as optical switches, modulators, and wavelength converters, that operate at very high speeds and low energies. To achieve these capabilities, however, requires plasmonic nanostructures with a strong nonlinear optical response.Recent theoretical work has shown that when surface plasmons interact with single quantum emitters the two systems can hybridize to form new coupled modes of light and matter. In this hybridized regime, a single plasmon can produce a nonlinear optical response, paving the way for nonlinear plasmonic circuits operating at the fundamental quantum energy limit. To date, however, this hybridized regime remains elusive because quantum emitters typically suffer from large dephasing due to phonons and spectral wandering. In this program, we will investigate the interaction between metallic nanostructures and indium arsenide quantum dots to study the hybridized regime and develop ultra-fast nonlinear and quantum devices. Indium arsenide quantum dots exhibit a spectrally pure emission making them ideal for achieving hybridization. We will use these high quality quantum emitters to demonstrate hybridization, and explore its nonlinear and quantum optical properties. This program could ultimately pave the way towards nanoscale photonic devices with ultra-low energy dissipation, as well as compact quantum circuits that provide exponential computational speedup and unconditionally secure communication. The program will also support an outreach effort that provides research opportunities for undergraduate and high school students.Technical DescriptionPlasmonic nanostructures can strongly enhance light-matter interactions by confining light to the nanoscale in the form of surface plasmon polaritons (or simply plasmons). Recently, it has been theoretically predicted that when a quantum emitter is placed in the high field region of a plasmonic nanostructure the two systems can hybridize. In this hybridized regime, the emitter and plasmon form new coupled modes that take on both atomic and photonic properties. These hybridized modes exhibit strong optical nonlinearities near the single photon level, making them a highly compelling system for developing opto-electronic and quantum devices with ultra-low power dissipation. Hybridization between single quantum emitters and plasmons has yet to be demonstrated because quantum emitters usually exhibit rapid dipole dephasing due to phonon scattering and spectral wandering. This dephasing destroys the quantum interference that creates the hybridized mode. We propose to overcome this problem using indium arsenide (InAs) quantum dots that exhibit a narrow and nearly transform limited optical emission, making them promising systems for attaining the hybridized regime. A key challenge to coupling these InAs quantum dots to metal nanostructures is that they are embedded in a gallium arsenide matrix and cannot be easily deposited onto plasmonic devices. We will address this challenge through a combination of device design and state-of-the-art nanofabrication techniques. We will characterize the linear and nonlinear properties of fabricated devices. We will then utilize the hybridized regime to demonstrate a nanophotonic optical transistor where a single absorbed control photon can switch many signal photons. We will also utilize the hybridized regime to create an interface between a single trapped spin in a quantum dot and a surface plasmon, which could serve as a fundamental building block for nanoscale quantum circuits. This program could ultimately pave the way towards nanoscale nonlinear photonic devices with ultra-low energy dissipation, and compact quantum circuits that provide exponential computational speedup and unconditionally secure communication.