EFRI ACQUIRE: Integrated Nanophotonic Solid State Memories for Telecom Wavelength Quantum Repeaters

摘要：非技术描述：安全数据通信对商业和国家安全至关重要。当前的加密方法依赖于计算硬度，假设对手的计算能力有限，无法破解加密。使用量子信息而不是经典信息操作的计算机进行量子计算挑战了这一范式，因为量子计算机的计算能力与现有计算机不同，确切的边界仍然未知。同时，使用量子技术的通信可以提供由物理基本定律保证的安全性，而不是计算难度。这是基于量子力学的“不可克隆定理”，该定理指出量子信息不能被复制，因此可以抵抗任何形式的窃听。目前量子通信系统的实现被限制在几百公里以内的距离，因为光通过光纤的传输在这些长度上会明显衰减。这远远不足以跨越大陆或海洋。传统的通信系统通过使用中继器来克服这个障碍，中继器是在长链路上周期性地增强信号强度的放大器。这种技术不能应用于量子信息，因为不可克隆定理禁止放大。已经开发出协议，使用可以存储量子信息的量子存储器无限期地扩展量子通信的范围。这些被称为“量子中继器”，尽管它们不放大信号，只是松散地类似于经典通信网络的中继器。量子中继器系统的基本组成部分已经在原理验证实验室实验中得到验证；然而，这种技术实际上不能扩展到大型系统。提议团队将为量子中继器开发可扩展的技术，包括新的量子存储器，集成和使用这些存储器的高效接口，以及用于量子通信的新协议。该项目的重点是设计光学纳米结构，以有效地与充当量子存储器的固体中的单原子杂质相连接，以及有效地检测和转换单光子。此外，该团队将探索量子信息系统的理论，以确定利用这些实验系统的特定功能的方法，这将为量子网络带来新的协议和编码。技术描述：该项目的总体目标是开发基于量子中继器架构的芯片级集成纳米光子组件，用于可扩展的远距离量子通信。该团队将解决ACQUIRE计划的所有三个重点，具体目标如下：1)量子水平的材料表征和工程，以开发新的固体类原子系统（钻石中的色中心，稀土离子），用作量子存储器和单光子源，以及设备工程，将这些系统与纳米光子腔和波导集成，以增强原子-光子相互作用；2)低损耗、宽带波导在硅衬底上的异构集成，实现波长转换器，作为高效量子存储器和室温探测器、可扩展光子对源和低损耗电光调制器的关键使能技术；3)采用绝热光纤锥形和波导三维锥形的低损耗光纤到芯片接口；4)基于正在研究的特定实验平台的量子中继器协议的理论发展和分析，以指导工程工作并确定权衡；5)利用光纤试验台平台同时演示了量子中继器协议的关键要素（包括自旋光子纠缠、长寿命量子存储的辅助核自旋纠缠、远程纠缠交换）。

Abstract Title: Development of quantum memory and photonic chip technologies for relaying long distance secure communications and connecting remote quantum networks Abstract:Non-technical description: Secure data communications are essential for commerce and national security. Current encryption methods rely on computational hardness, assuming that an adversary has limited computational power to break the encryption. Quantum computing using computers operating on quantum information instead of classical information challenges this paradigm, since the computational power of quantum computers is different from that of existing computers, with the exact boundaries still unknown. At the same time, communication using quantum technologies can provide security guaranteed by the fundamental laws of physics instead of computational hardness. This is based on the "no-cloning theorem" of quantum mechanics, which states that quantum information cannot be copied and is therefore resistant to eavesdropping in any form. Current implementations of quantum communication systems are limited to distances less than several hundred kilometers because the transmission of light through optical fibers is attenuated significantly at these lengths. This is vastly insufficient to reach across a continent or an ocean. Classical communications systems overcome this obstacle by using repeaters, which are amplifiers that boost the signal strength periodically over a long link. This technology cannot be applied to quantum information, because amplification is forbidden by the no-cloning theorem. Protocols have been developed to extend the range of quantum communications indefinitely using quantum memories that can store quantum information. These are referred to as "quantum repeaters", although they do not amplify signals and are only loosely analogous to repeaters for classical communications networks. The basic elements of a quantum repeater system have been demonstrated in proof-of-principle laboratory experiments; however, this technology cannot practically be scaled to large systems. The proposing team will develop scalable technologies for quantum repeaters, including new quantum memories, efficient interfaces to integrate and use those memories, and new protocols for quantum communication. The project focuses on designing optical nano-structures to efficiently interface with single-atom impurities in solids that act as quantum memories, as well as to efficiently detect and frequency-convert single photons. Additionally, the team will explore the theory of quantum information systems to identify ways to leverage the specific capabilities of these experimental systems, which will result in new protocols and encodings for quantum networks.Technical description: The overall goal of this project is to develop chip-scale, integrated, nanophotonic components for scalable, long-distance quantum communication based on a quantum repeater architecture. The team will address all three thrusts of the ACQUIRE program with the following specific goals: 1) Material characterization and engineering at the quantum level to develop new atom-like systems in the solid state (color centers in diamond, rare earth ions) to use as quantum memories and single photon sources, and device engineering to integrate these systems with nanophotonic cavities and waveguides to enhance atom-photon interaction; 2) Heterogeneous integration of low loss, wideband ÷(2) waveguides on silicon substrates for realizing wavelength converters as a key enabling technology for efficient quantum memories and room temperature detectors, scalable photon pair sources, and low loss electro-optic modulators; 3) Low loss fiber-to-chip interfaces using adiabatic fiber tapering and waveguide 3D tapering; 4) Theoretical development and analysis of quantum repeater protocols based on specific experimental platforms being studied, in order to guide engineering efforts and identify trade-offs; 5) Simultaneous demonstration of key elements of quantum repeater protocols (including spin-photon entanglement, entanglement with ancilla nuclear spins for long-lived quantum memories, and remote entanglement swapping) using a fiber test-bed platform.