Multimode integrated time-frequency quantum photonics

量子物理处于一场技术革命的中心，这场革命有望使信息和通信技术(ICT)从安全通信、提高测量精度、大容量模拟和计算转变为仅使用经典资源无法实现的目标。这些量子增强技术将显著提高安全传输和处理日益增长的数据量的能力，这些数据是全球经济的基础。模拟复杂系统的能力，既包括量子系统，也包括经典系统，可以创造出效率更高的新功能材料，从设计药物到太阳能电池。此外，测量灵敏度的提高为探测以前无法访问的基础物理开辟了道路，以及更实际的应用，如微光光谱学。光将在光谱学、成像、通信和计算等许多量子技术中发挥核心作用。当寻址单个光子时，信息通常被编码为每个传输的光子一个量子比特(或量子比特)的信息。然而，这严重限制了当前方法对小尺寸的信息处理能力。最近可以实现的一种增加量子光学系统复杂性的方法是利用集成的量子光子学，在硅芯片上产生、引导和操纵光子。然而，这些技术仍然依赖于将信息编码为量子比特，并且没有利用单个光子的丰富结构。这个项目将采用一种新的方法来编码每个光子增加的信息量，从而实现显著增加的系统复杂性。为了增加用于集成光子学的单光子的信息容量，该项目将专注于在单个光子的时间-频率状态中编码信息，其中光子的时间形状和颜色携带信息。这种方法与传统ICT中使用的方法类似，例如波长和时分多路复用，其中信息以光脉冲的波长(颜色)或到达时间进行编码。牛津大学在光纤光子源和集成量子光子学方面的最新发展使这种新方法成为可能，这种光子学允许对单个光子进行确定性的频率控制。通过在一个综合平台上增加每个光子的信息容量，该项目旨在实现量子增强技术的重大进步。在更远的地方，在该项目期间开发的微光时频传感技术可用于从光谱学到光网络诊断的各种应用

Quantum physics is at the centre of a technological revolution that promises to transform information and communications technologies (ICT) from secure communications, enhanced precision in measurement, high-capacity simulation and computation beyond that capable using only classical resources. These quantum-enhanced technologies will significantly increase the capacity to securely transmit and process the ever-rising volumes of data on which the global economy is based. The ability to simulate complex systems, both quantum and classical, could allow creation of new functional materials ranging from designer drugs to solar cells with improved efficiency. Furthermore, improved sensitivity in measurements opens paths to probe fundamental physics previously not accessible, as well as more practical applications such as low-light-level spectroscopy. Light will play a central role in many of these quantum technologies such as spectroscopy, imaging, communications, and computation. When addressing individual photons, information is most often encoded as one quantum bit (or qubit) of information per transmitted photon. However, this severely limits the information processing capacity of current approaches to small sizes. One recent approach to increase the complexity of quantum optical systems that can be achieved utilizes integrated quantum photonics, in which photons are generated, guided and manipulated on silicon chips. However, these techniques still rely on encoding information as qubits and do not take advantage of the rich structure of individual photons. This project will take a new approach to encoding an increased amount of information per photon, and thus allow significantly increased system complexity to be achieved.To increase the information capacity of single photons for integrated photonics this project will focus on encoding information in the time-frequency state of individual photons, in which the temporal shape and colour of the photon carry the information. This approach parallels methods used in classical ICT such as wavelength- and time-division multiplexing where information is encoded in the wavelength (colour) or arrival time of light pulses. This new approach is made possible by recent developments at Oxford in fibre-based photon sources and integrated quantum photonics, which allow deterministic frequency control of single photons. By moving to this regime of increased information capacity per photon on an integrated platform, the project aims to enable significant advances in quantum-enhanced technologies. Further afield the techniques for low-light-level time-frequency sensing developed during the project could be utilized in a diverse range of applications from spectroscopy to optical network diagnostics