Charge quantum interference device and applications

该项目旨在开发一种新型量子器件-电荷量子干涉器件(CQUID)的技术，并演示其操作。这是一种新型的量子传感器，它可以探测超低的电荷，并减少反作用，具有潜在的广泛应用前景。该项目的重点应用将是实现新的电流量子标准的原型。在我们以前的工作中，我们展示了超导的一种新的基本现象--相干量子相移(CQPS)--这是新的CQUID器件的基础。这种效应是在一种新型材料--高度无序薄膜超导体--的纳米线上发现的。CQUID的作用与众所周知的超导量子干涉装置(SQUID)相反。这两种设备都依赖于量子干涉效应。SQUID是基于超导回路中电流(超导电流)的量子干涉，超导回路中的两个隧道结对所施加的磁通量敏感。相比之下，CQUID是基于通过两根纳米线的一对隧道磁通流的量子干涉，并且对感应电荷很敏感。因此，CQUID的核心是磁通量量子的隧道结。这对约瑟夫森结是双重的，约瑟夫森结是库珀对的隧道结。CQUID的开发将特别为计量应用铺平道路。相干磁通隧穿将是新的电流量子标准的核心，该标准的原型是该项目的最终目标。这一量子电流标准将允许在单电子水平上精确测量电流量。作为一类新的量子传感器，它也将在本项目之外的纳米电子领域发挥更广泛的作用。建立量子电流标准的原型是一项具有挑战性的目标：我们将从理论上分析和模拟该器件；为可控相滑结的制造开发一个强大的纳米工艺；研究阻碍当前标准运行的耗散和退相机制；了解所谓的准粒子中毒并将其影响降至最低；模拟、设计和研究相移电流标准的最佳环境，例如紧凑的混合电感(来自高度无序的薄膜和约瑟夫森结)。至关重要的是，我们将演示所谓的逆Shapiro阶跃，即当相滑结(超导纳米线)被特定频率的微波照射时，在器件的电流-电压特性中观察到的电流平台。该技术将利用皇家霍洛威(SuperFab)新建立的纳米制造设施进行开发，该设施已在EPSRC和机构资本投资的联合支持下建设，将于2019年初全面运营。SuperFab配备了专门用于超导量子系统技术的独特制造设施。该项目的重点是超导量子技术，将成为英国量子技术计划的一部分。一个重要的项目合作伙伴是国家物理实验室，在那里，计量专业知识将在新量子电流标准原型的开发和优化中发挥重要作用。

The project aims to develop the technology of a novel type of quantum device, the Charge Quantum Interference Device (CQUID), and demonstrate its operation. This is a new quantum sensor, which detects ultralow charges with reduced backaction, with potentially a broad range of applications. The focus application of this project will be to realize the prototype of a new quantum standard for electrical current. In our previous work we demonstrated the new and fundamental phenomenon of superconductivity - Coherent Quantum Phase Slip (CQPS) - which is the basis of the new CQUID device. The effect was discovered in nanowires patterned in a new class of materials - highly disordered thin film superconductors. The CQUID acts in the opposite way to the well known superconducting quantum interference device (SQUID). Both devices rely on the quantum interference effect. A SQUID is based on the quantum interference of electric currents (supercurrents) in a superconducting loop with two tunnel junctions sensitive to the applied magnetic flux. By contrast, a CQUID is based on the quantum interference of a pair of tunnelling magnetic flux flows via two nanowires and sensitive to the induced electric charge. Thus the core of the CQUID is the tunnel junction for magnetic flux quanta. This is dual to a Josephson junction, which is the tunnel junction for a Cooper pair. The development of CQUIDs will particularly pave the way for metrological applications. The coherent flux tunnelling will be the core of a new quantum standard for electrical current, the prototype of which is the ultimate objective of this project. This quantum current standard will allow precise measurement of the flow of electricity at the single electron level. As a new class of quantum sensor, it will also play a wider role in nanoscale electronics beyond this project. Building the prototype of the quantum current standard is a challenging goal: we will theoretically analyse and simulate the device; develop a robust nano-technological process for the controllable phase-slip junction fabrication; investigate mechanisms of dissipation and dephasing hindering operation of the current standard; understand so-called quasiparticle poisoning and minimise its effect; simulate, design and investigate an optimal environment for the phase-slip current standards, such as compact hybrid inductances (from highly disordered films and Josephson junctions). Crucially, we will demonstrate the so-called inverse Shapiro steps, which are current plateaus in the current-voltage characteristic of the device, observed when the phase-slip junction (a superconducting nano-wire) is irradiated by microwaves of a particular frequency. The technology will be developed exploiting the newly established nano-fabrication facilities at Royal Holloway (SuperFab), which has been built with joint EPSRC and institutional capital investment support, and which will start full operation in early 2019. SuperFab is equipped with unique fabrication facilities dedicated specifically for technologies of the superconducting quantum systems. This project, with a focus on superconducting quantum technology, will form part of the UK Quantum Technology Programme. An important project partner is the National Physical Laboratory, where expertise in metrology will play an important role in the development and optimisation of the new quantum current standard prototype.