Quantum Computing with Superconducting Gatemon Qubits

超导transmon量子位是用于构建包含~100个量子位的原型量子计算机的有吸引力的平台。为了超越这一点，并建立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族半导体的门控量子比特是最近创新的压控transmon，具有缩放优势，但其性能目前受到微波损耗的限制。为了提高性能，我们将通过测量品质因子的功率、温度和时间依赖性来研究包括Al/Nb/InP的III-V结构中的损耗机制。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Si衬底上生长的压控半导体，例如石墨烯或V-VI拓扑绝缘体。强自旋轨道相互作用在后者也使它有可能实现马约拉纳物理和一个目的是测试拓扑保护的松弛时间在马约拉纳transmon-MRC。

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.