Magnetically-induced topological phases in superconductor-semiconductor qubits

超导电路是实现量子计算机的主要方法之一。我们最近的工作已经确定，半导体可以用来操纵超导量子比特，并提高了扩展到几百[1]以上的前景。此外，超导体可以在半导体中诱导电子物质的特殊相位，这可以用来创造一种革命性的量子比特，这种量子比特受环境干扰的影响较小。在许多这样的方案中，电子需要处于强大的全局磁场中，这会削弱量子比特的超导特性和性能。解决这个问题的一种方法是在半导体[3]内部或附近使用局部铁磁薄膜和掺杂剂。这个博士项目的目标是实现这种零场拓扑量子比特。具体来说，我们将使用纳米磁体阵列的螺旋场在近似的III-V纳米结构中诱导拓扑相，并演示磁掺杂V-VI半导体之间的约瑟夫森耦合。然后，我们将这些约瑟夫森元件集成到超导量子比特中，并使用电路量子电动力学来显示相对于传统非拓扑量子比特的增强弛豫和减相时间。

Superconducting circuits are one of the leading approaches to realising a quantum computer. Our recent work has established that semiconductors can be used to manipulate superconducting qubits and improve the prospects for scaling beyond a few hundred [1]. Furthermore, the superconductor can induce special phases of electronic matter in the semiconductor that can be used to create a revolutionary type of qubit that is less affected by disturbances in the environment [2]. In many of these schemes the electrons need to be in strong global magnetic fields that weaken the superconducting properties and performance of the qubit. One way around this is to use local ferromagnetic films and dopants in or nearby the semiconductor [3]. The aim of this PhD project is to realise such zero-field topological qubits. Specifically, we will use the helical field from nanomagnet arrays to induce topological phases in proximitised III-V nanostructures and demonstrate Josephson coupling across magnetically-doped V-VI semiconductors. We will then integrate these Josephson elements into a superconducting qubit and use circuit quantum electrodynamics to show enhanced relaxation and dephasing times relative to conventional non-topological qubits.