International Network on Quantum Annealing (INQA)

量子退火（QA）是通用基于门的量子计算（GBQC）的一种特定于应用的替代范例。QA最初被提出的应用是优化，尽管最近在量子模拟和机器学习中的应用也被提出。与GBQC相比，QA对底层量子比特的相干性要求不那么严格。这使得实验人员能够使用QA演示许多不同的优化用例原理证明，利用D-Wave Systems开发的基于超导通量量子位的退火系统。这些应用包括材料模拟、金融投资组合优化、流量路由、欺诈检测、电路故障诊断和网站推荐引擎。尽管如此，目前还缺乏（如果有的话）任何真实的世界应用的任何量子加速的实验证据，并且至少可以肯定的是，仅仅增加现有硬件中的通量量子比特的数量而没有任何新的定性设计特征将永远不会导致缩放加速。因此，在美国，英国，欧盟和日本建立了几个全球合作，以确定可以在量子退火设备的未来实现中添加哪些定性特征，这些特征将通过与经典基准的比较来实现转换缩放加速（至少对于某些类别的困难问题）。与现有的D-Wave实现相比，这些合作的关键在于前者对相干量子比特的关注。例如，在美国的QAFS计划中，使用麻省理工学院林肯实验室开发的铝电容分流通量量子比特实现了相干寿命，这两种量子比特都比D-Wave目前使用的铌量子比特长三个数量级以上，并且超过了约1微秒的典型退火持续时间。完全相干退火可以提供许多好处，最值得注意的是通过最小间隙过渡的能力，最小间隙在困难（即小间隙）问题中充当计算加速的瓶颈。完全相干退火在精神上也更接近于封闭系统绝热量子计算（AQC），其中有一个被证明与GBQC等价（因此可以证明量子加速）。国际量子退火网络（INQA）将首次建立一个机制，通过该机制，四个全球合作组织将共同分享技术和知识专长，并批判性地分析量子退火理论和实验研究的发展。该网络将由UCL的Paul Warburton教授领导，他是英国量子计算和模拟（QCS）中心和最近宣布的QEVEC项目的共同研究者。他还曾是美国领导的QEO和QAFS合作的联合研究员。其他被INQA命名为网络参与者的英国研究人员是格拉斯哥大学（QCS Hub和EU-AVAQUS）的Martin Weides教授，斯特拉斯克莱德大学（QCS Hub和QEVEC）的Viv Kendon教授，达勒姆大学（QCS Hub和QEVEC）的Nick Chancellor博士和UCL的Andrew绿色教授。该网络将每周举办在线技术研讨会，为合作大学之间的国际交流访问提供资金，并举办年度会议。这些会议将与现有的年度AQC会议（将由INQA部分赞助）交错，以便每年提供两次退火专用科学会议。

Quantum annealing (QA) is an application-specific alternative paradigm to universal gate-based quantum computation (GBQC). The application for which QA was originally proposed is optimisation, though more recently applications in quantum simulation and machine learning have also been proposed. QA makes less stringent demands on the coherence of the underlying qubits than does GBQC. This has enabled experimentalists to demonstrate many diverse optimisation use-case proofs of principle using QA, exploiting the superconducting flux-qubit-based annealing system developed by D-Wave Systems. Such applications include materials simulation, financial portfolio optimisation, traffic routing, fraud detection, circuit fault diagnosis and website recommendation engines. Nevertheless at present there is scant (if any) experimental evidence of any quantum speedup for any real world application, and it is at least arguable that merely increasing the number of flux qubits in the existing hardware without any new qualitative design features will never lead to a scaling speedup. Several global collaborations have therefore been set up in the US, UK, EU and Japan to identify what qualitative features could be added to future implementations of quantum annealing devices which would enable a transformational scaling speedup (at least for some class of hard problems) by comparison with classical benchmarks. A key discriminator for these collaborations by comparison with the existing D-Wave implementation is the focus of the former on coherent qubits. In the QAFS programme in the US, for example, use of the aluminium capacitively-shunted flux qubits developed at MIT Lincoln Lab has enabled coherence lifetimes which are both more than three orders of magnitude longer than the niobium qubits currently used by D-Wave and which exceed the typical anneal durations of around 1 microsecond. Fully coherent annealing may offer a number of benefits, most notable being the ability to transition through the minimum gap which acts as a bottleneck for computational speedup in hard (i.e. small gap) problems. Fully coherent annealing is also closer in spirit to closed-system adiabatic quantum computation (AQC) for which there is a proven equivalence to GBQC (and therefore provable quantum speedup). The International Network in Quantum Annealing (INQA) will for the first time establish a mechanism by which four global collaborations come together to share technical and intellectual know-how and critically analyse developments in theoretical and experimental research in quantum annealing. The network will be led by Prof. Paul Warburton of UCL, who is a co-investigator in the UK's Quantum Computation and Simulation (QCS) Hub and in the recently-announced QEVEC project. He was also previously a co-investigator in the US-led QEO and QAFS collaborations. Other UK researchers who are named network participants in INQA are Prof. Martin Weides of the University of Glasgow (QCS Hub and EU-AVAQUS), Prof. Viv Kendon of Strathclyde University (QCS Hub and QEVEC), Dr Nick Chancellor of Durham University (QCS Hub and QEVEC) and Prof. Andrew Green of UCL. The network will host weekly on-line technical seminars, offer funding to enable international exchange visits between collaborating universities, and run annual conferences. These conferences will be interlaced with the existing annual AQC conferences (which will be part-sponsored by INQA) so as to provide two annealing-specific scientific meetings per year.