Fibre-integrated ORCA quantum memory

光子量子网络将实现量子计算、保密通信和增强的传感能力，在环境条件下以高带宽运行。为了充分利用光子网络的潜力，需要对光信号进行切换和重新定时的能力。但事实证明，这对量子信号来说是一个挑战，因为放大会在量子水平上增加噪声，因此必须小心消除无源损耗。传统的基于电光相位调制和体非线性的光子交换和存储解决方案损耗太大或不适合在单个光量子的水平上操作。一个有前途的途径，快速，低损耗，量子兼容的光纤集成开关器件是原子蒸汽纳入中空纤维。这是博士项目的重点。在牛津大学最近的工作中，GHz带宽的光子通过非共振级联吸收（ORCA）存储在温暖的碱蒸气中并从中检索[Kaczmarek et al. Phys. Rev. A 97.4 042316（2018）]。此后，Weizmann研究所[Finkelstein et al. Science advances 4.1 eaap8598（2018）]和阿德莱德大学[Perella et al.未发表的通信（2018）]实施了相同的方案。在巴斯的平行工作中，与NQIT和TMD有限公司合作，我们探索了使用空心纤维蒸气室进行磁力测定和原子钟。在这个项目中，学生将进一步发展这项初步工作，目的是将光纤蒸汽电池直接拼接到单模光纤中，并通过ORCA在量子水平上展示光纤集成光存储。这项工作将与Pete Mosley博士（CPPM主任）的团队密切合作进行，并成为英国量子技术计划的一部分，在量子模拟和量子计算第二阶段中心的支持下，巴斯物理正在参与该项目。关于该项目的具体内容：第一项任务将是建立一个脉冲激光系统，通过ORCA协议实现Rb蒸气的存储和检索。下一步，将建立一个真空系统，以加载Rb到中空纤维。然后，我们将研究如何将中空光纤拼接成单模光纤，使用中间模式转换光纤来匹配芯直径。最后，我们将研究在Rb装载后，在氦气超压下进行拼接，以便Rb被密封到中空纤维中。如果时间允许的话，该项目的最终目标是演示在光纤集成存储器中存储和检索脉冲。

Photonic quantum networks would enable quantum computing, guaranteed-secure communications and enhanced sensing capabilities, running at high bandwidths in ambient conditions To exploit the full potential of photonic networks, the capability to switch and re-time optical signals is required. But this has proved challenging for quantum signals, since amplification adds noise at the quantum level, and so passive losses must be carefully eliminated. Conventional photonic switching and storage solutions based on electro-optical phase modulation and bulk non-linearities are too lossy or not suitable for operation at the level of individual light quanta. A promising route to fast, low-loss, quantum-compatible fibre-integrated switching devices is the incorporation of atomic vapour into hollow fibres. This is the focus of the proposed PhD project. In recent work at Oxford, GHz bandwidth photons were stored in, and retrieved from, a warm alkali vapour, via off-resonant cascaded absorption (ORCA) [Kaczmarek et al. Phys. Rev. A 97.4 042316 (2018)]. The same protocol has since been implemented at the Weizmann Institute [Finkelstein et al. Science advances 4.1 eaap8598 (2018)] and at the University of Adelaide [Perella et al. unpublished communication (2018)]. In parallel work at Bath, in partnership with NQIT and TMD Ltd., we have explored the use of hollow-fibre vapour cells for magnetometry and atomic clocks. In this project, the student will further develop this initial work, with the aim of splicing fibre vapour cells directly into single-mode fibres, and demonstrating fibre-integrated light storage via ORCA at the quantum level. The work will proceed in close collaboration with the group of Dr. Pete Mosley (CPPM director) and forms part of the UK Quantum Technology Programme, under the aegis of the Phase II Hub in Quantum Simulation and Quantum Computation, in which Bath Physics is participating.On the specifics of the project: the first task will be to build a pulsed laser system to enable storage and retrieval in Rb vapour via the ORCA protocol. Next, a vacuum system to load Rb into hollow fibre will be built. We will then look at splicing our hollow fibres to single-mode fibre, using an intermediate mode conversion fibre to match the core diameters. Finally we will investigate performing the splice after Rb loading, under helium overpressure, so that Rb is sealed into the hollow fibre. The ultimate aim of the project, time permitting, is to demonstrate the storage and retrieval of pulses inside a fibre-integrated memory.