Toward a Large-Scale Superconducting Quantum Computer: Error Management and Scalability

实用的量子计算机比以往任何时候都更接近现实。在许多实现方案中，囚禁离子、半导体器件和超导量子电路是实现约100-100000量子比特的中型和大型量子计算机的最有前途的候选方案。超导量子比特已经被集成到约50个量子比特的阵列中，并且原则上可以进一步集成。然而，由于不完美的材料或不适当的工程造成的耗散现象可能会导致量子比特失败，并且到目前为止，仍然是一个主要的挑战。此外，从中型系统转移到大规模系统将需要真正可扩展的经典量子比特布线和控制技术，而这些技术目前尚不存在。 致力于实用量子计算机的社区在过去五年中发生了戏剧性的变化。IBM和谷歌等大型企业正在投资数亿美元来改进和扩大量子比特阵列。为了具有竞争力，临床研究方案的选择势在必行。经典的集成电路产业应该是一个例子。大型企业建立一个完整的计算平台所需的硬件和软件；研究实验室调查开放的科学和技术挑战，并找到解决方案，然后被大公司采用。 我的研究计划的长期愿景是减少量子比特错误，并为大型量子计算机开发可扩展的技术。两个主要目标是： O1)错误管理： A.通过集成一种新的超导电路：口袋谐振器，消除由于不完美材料造成的耗散。 B.实现一个新的量子比特：口袋量子比特。 O2)可扩展性： A.为大规模量子计算机开发一种新的量子比特布线技术：完全垂直互连的管脚芯片键合。 B.使用量子比特对针芯片键合进行基准测试。 超导片上器件的材料缺陷是由于量子比特附近的氧化层的存在。口袋量子比特是一种新型的超导设备，我们将量子比特的能量存储在一个仅受不需要的层轻微影响的空间区域，而不是去除氧化层。 管脚芯片连接是我发明的一种新的量子比特布线技术。这项技术使操作超过100000个量子比特的二维阵列成为可能，允许从上方到达阵列中的任何量子比特，而不是像目前使用传统技术所做的那样横向进行。如果一个正方形芯片包含N×N个量子比特，从上面访问这些量子比特可以让我们达到N个量子比特，而不是从两边只有4N个量子比特。 加拿大，特别是滑铁卢，已经创造了一个强大的“量子生态系统”。我的研究计划旨在加强这一努力，朝着实用的量子计算技术的方向发展。这将产生一批高技能的加拿大学生，他们在一个迅速发展的研究领域拥有专业知识。

Practical quantum computers are closer to reality than ever before. Among many implementations, trapped ions, semiconducting devices, and superconducting quantum circuits are among the most promising candidates to implement medium- and large-scale quantum computers with ~100-100000 qubits. Superconducting qubits have already been integrated in arrays of ~50 qubits and can in principle be further integrated. However, dissipation phenomena due to imperfect materials or inadequate engineering can cause a qubit to fail and, to date, continue to be a major challenge. Additionally, moving from medium- to large-scale systems will require truly scalable classical qubit wiring and control techniques that are not yet available. The community working on practical quantum computers has evolved dramatically in the last five years. Major ventures such as IBM and Google are investing hundreds of millions of dollars to improve and scale up qubit arrays. In order to be competitive, it is imperative to choose a research plan clinically. The classical integrated circuit industry should serve as an example. Major ventures build the hardware and software required for a complete computing platform; research labs investigate the open scientific and technological challenges and find solutions that are then adopted by the large companies. The long-term vision of my research program is to reduce qubit errors and develop scalable technologies for a large-scale quantum computer. The two main objectives are: O1) Error management: a. Banish dissipation due to imperfect materials by integrating a novel superconducting circuit: The pocketmon resonator. b. Realize a new qubit: The pocketmon qubit. O2) Scalability: a. Develop a new qubit wiring technique for a large-scale quantum computer: Pin-chip bonding for fully vertical interconnects. b. Benchmark pin-chip bonding with qubits. Material imperfections in superconducting on-chip devices are due to the presence of oxidized layers in proximity of the qubits. The pocketmon qubit is a new type of superconducting device where, instead of removing the oxidized layers, we store the qubit energy in a region of space that is only marginally affected by the unwanted layers. Pin-chip bonding is a novel qubit wiring technique that I invented. This technique makes it possible to operate two-dimensional arrays with more than 100000 qubits, permitting to reach any qubit in the array from above instead of laterally, as presently done with traditional techniques. If a square chip contains NxN qubits, accessing the qubits from above allows us to reach N2 qubits instead of just 4N qubits from the sides. Canada in general and, in particular, Waterloo have already created a strong “quantum ecosystem.” My research program aims at strengthening this effort in the direction of practical quantum computing technologies. This will generate a strong class of highly skilled Canadian students with expertise in a rapidly blooming field of research.