Chip-based Quantum Networking

该项目属于EPSRC量子技术研究领域。该项目包括设计、模拟和测试用于纠缠分配网络的基于集成光子学的纠缠光子对源。其目的是在Bell态产生适合用于纠缠交换过程的光子。信号源也是为了与现有的光纤基础设施兼容，以便它可以部署在类似于现有的经典因特网的多用户/大规模网络中。创建如此大规模的量子网络的希望是创建安全的通信通道，使其能够抵御窃听者和那些希望将信息用于恶意目的的人。目前互联网上使用的数据加密方法并不安全，不能免受量子计算机的威胁。通过使用纠缠等量子属性，量子计算机有可能以指数级的速度计算某些类型的问题，速度比经典计算机快。一个这样的问题是大素数的因式分解，这对于传统计算机来说目前花费的时间是不可行的，所以这样的大素数被用来加密传输密钥。通过使用量子属性，量子密钥分发(QKD)提供了一种传输加密密钥的方法，这些密钥即使是在量子计算机的威胁下也是安全的。大规模量子网络最紧迫的用途是在多个并发用户之间实现量子密钥分发。到目前为止，大规模量子网络的困难在于高损耗和不稳定，这阻碍了构建此类网络的能力。芯片规模的光子对源将通过提供具有更长相干时间的光子来帮助缓解一些稳定性问题。与使用传统使用的大宗光学光源相比，这提高了在纠缠分配网络中使用的纠缠交换过程的机会。创建这样一个源的过程首先需要集成硅光子学理论、量子理论、量子信息理论和量子密钥分发协议的知识。它将需要关于芯片中使用的特定光子组件的知识，特别是如何对组件进行建模和仿真，以便指定性能特征。将有大量的实验室工作，以测试和表征个别组件，然后测试和表征整个芯片后，它已经被制造。实验室工作将需要安全和称职地使用光纤、激光和单光子探测器。

This project falls within the EPSRC quantum technologies research area. This project involves designing, simulating and testing an integrated photonics based entangled photon pair source for an entanglement distribution network. The aim is to generate photons in a Bell state that are suitable to be used in an entanglement swapping process. The source is also to compatible with existing fibre-optic infrastructure so that it can be deployed in a many-user/large-scale network similar to that of the existing classical internet. The hope of creating such a large-scale quantum networks is to create secure channels of communications that are resilient to eavesdroppers and those who wish to use information for malicious purposes. Current data encryption methods used in the Internet are not safe from the threats of quantum computers. Quantum computers have the potential, by using quantum properties such as entanglement, to compute certain types of problems exponentially faster than a classical computer. One such problem is the factoring of large prime numbers, which currently takes an unfeasible amount of time for a classical computer so such large prime numbers are used to encrypt transmission keys. By also using quantum properties, quantum key distribution (QKD) provides a means of transmitting encryption keys that are secure from even the threat of quantum computers. The most imminent use of large-scale quantum networks is to implement QKD across many concurrent users. As of now the difficulties of large-scale quantum networks are high losses and instability that are hindering the ability to build such networks. A chip-scale photon-pair source will help alleviate some of the stability issues by providing photons with a longer coherence time. This improves the chances of an entanglement swapping process that is used in entanglement distribution networks compared to using a bulk optics source that is traditionally used. The process of creating such a source will first require knowledge of theory of integrated silicon photonics, quantum theory, quantum information theory and QKD protocols. It will require knowledge on specific photonic components used in the chip, specifically how to model and simulate the components in order to specify performance characteristics. There will be extensive lab work in order to test and characterise individual components and thereafter the full chip after it has been fabricated. The lab work will require safe and competent use of fibre optics, lasers and single photon detectors.