Bright sources of quantum light for efficient entanglement distribution

人类目前正在经历一场重大的技术革命，其中量子物理学的微妙概念，如状态叠加和纠缠，现在开始用于重大的新技术。在所有正在探索的“量子赋能”技术中，基于光子的量子通信具有关键的社会相关性，因为它促进了通信各方之间绝对安全的数据传输。与此同时，由于新型半导体光子纳米材料的发展，对凝聚态系统中量子（自旋）自由度的新理解，以及将量子光学工具箱中的技术应用于固态系统的可能性，基础科学的最新进展已经将其推向了现实世界的应用。虽然许多令人印象深刻的概念验证演示已经完成，但距离可扩展性和光子损耗仍然是阻止光子驱动量子计算机或网络发展的两个主要问题。提出了利用量子中继器（QR）规避光子损耗的建议。然而，大多数QR协议的实现需要高性能量子存储器的可用性，具有出色的写入/读出效率和超过毫秒的非常长的内存时间。寻找一种同时促进高光子产生和相互作用速率，提供长记忆时间，而且可扩展的物理系统仍然是阻碍进一步发展的主要科学挑战。最近，新型的多光子量子态——所谓的簇态或图态被提出作为分布式量子技术的一种全新资源。这些状态由一个包含许多光子的光脉冲组成，这些光子在一个高度纠缠的状态下制备，每个光子的量子态与其他光子的量子态错综复杂地联系在一起。与单个、分离的光子不同，簇态具有内在的高度冗余；由于光子不可避免地会丢失，量子纠缠仍然可以通过分裂簇态并向每个通信方发送部分来在通信方之间共享。通过这种方式，只要一些光子到达通信方，纠缠仍然可以分布。这种新颖的方法完全绕过了对高性能量子存储器的需求，高性能量子存储器是迄今为止阻碍可靠的高速率纠缠分布技术发展的主要障碍之一。这个DIP项目汇集了来自以色列和德国三个主要机构的物理系和电子工程系的五位科学家，他们在实验和理论方面都有工作。参与研究的研究人员将设计和测试用于高速率纠缠分布的新协议，并实现高性能、光寻址和电可调的半导体自旋系统。

Humankind is currently experiencing a major technological revolution in which the subtle concepts of quantum physics, such as state-superposition and entanglement are now starting to be used for major new technologies. Amongst all the “quantum enabled” technologies being explored, photon-based quantum communication is of key-societal relevance since it facilitates absolutely secure data transmission between communicating parties. At the same time, recent stepchanging advances in fundamental science have now pushed it closest to real-world application, driven by progress in the development of novel semiconductor photonic nanomaterials, new understandings of quantum (spin) degrees of freedom in condensed matter systems and the possibility to apply techniques from the quantum optics toolbox to solidstate systems. While a number of impressive proof-of-concept demonstrations have already been made, distance scalability and photon-loss remain two of the primary issues that stop the development of photon powered quantum computers or networks. Suggestions to circumvent photon loss have been made using quantum repeaters (QR). However, the implementation of most QR protocols calls for the availability of performant quantum memories with exceptional write-in / read-out efficiencies and very long memory times exceeding milliseconds. Finding one physical system that simultaneously facilitates high photon-generation and -interaction rates, offers long memory times and, moreover, is scalable remains a major scientific challenge that has inhibited further progress.Recently, new types of multi-photon quantum states – so called cluster or graph states have been proposed as an entirely new resource for distributed quantum technologies. These states consist of a pulse of light containing many photons prepared in a highly-entangled state for which the quantum state of each photon is intricately linked to the others. Unlike single, separated photons, cluster states have an inbuilt high degree of redundancy; as photons are inevitably lost, quantum entanglement can still be shared among communicating parties by splitting cluster states and sending parts to each of the communicating parties. In this way, providing that some of the photons arrive at the communicating parties, entanglement can still be distributed. This kind of novel approach completely circumvents the need for highly performant quantum memories, one of the major obstacles that has hindered the development of reliable technologies for high-rate entanglement distribution to date.This DIP project brings together five scientists from three leading institutions in Israel and Germany in departments of Physics and Electronic Engineering, working in both experiment and theory. The participating researchers will design and test new protocols for high-rate entanglement distribution and realize highly performant, optically addressable and electrically tunable semiconductor-based spin-systems incorporated (...)