Quantum Computing with Superconducting Gatemon Qubits

超导跨量子比特是构建约100个量子比特的量子计算机原型的一个有吸引力的平台。为了超越这一点，建造强大到足以破解安全加密或模拟小分子的量子计算机，有必要提高一致性和可扩展性。基于III-V半导体的盖特蒙量子比特是最近发明的一种压控传输方式，具有可伸缩的优点，但目前它们的性能受到微波损耗的限制。为了提高性能，我们将通过测量质量因子的功率、温度和时间依赖关系来研究Al/Nb/InP组成的III-V结构的损耗机制。初步测量将在国家物理实验室进行。我们还将探索可以在低损耗硅衬底上生长的压控半导体，例如石墨烯或V-VI拓扑绝缘体。后者中强烈的自旋-轨道相互作用也使实现Majorana物理成为可能，其中一个目标是在Majorana Transmon-MRC中测试拓扑保护的驰豫时间。

Superconducting transmon qubits are an attractive platform for building a prototype quantum computer comprising ~100 qubits. In order to go beyond this and build quantum computers powerful enough to break secure encryption or simulate small molecules, it will be necessary to improve coherence and scalability. Gatemon qubits based on III-V semiconductors are a recently innovated voltage-controlled transmon that offers advantages with scaling, but their performance is currently limited by microwave losses. In order to improve performance we will study loss mechanisms in III-V structures comprising Al/Nb/InP by measuring the power, temperature and time-dependence of quality factors. Initial measurements will be performed at the National Physical Laboratory. We will also explore voltage-controlled semiconductors that can be grown on low-loss Si substrates, for instance, graphene or V-VI topological insulators. The strong spin-orbit interaction in the latter also makes it possible realise Majorana physics and and one aim is to test for topologically-protected relaxation times in a Majorana transmon-MRC.