Gate-controlled nanowire Josephson junctions in the microwave regime: Spectroscopy and coherence of harmonic and anharmonic resonators

该项目的目标是实验实现电控transmon量子位（qubit）。量子位电路将基于超导体/半导体纳米线约瑟夫森结，其中临界电流由底栅或侧栅电极控制。因此，基于栅控三极管的结将用作量子位电路中的场可调谐非线性电感。至于纳米线，将采用体InAs纳米线或GaAs/InAs核/壳纳米线。后一种结构将提供额外的面内通量控制。纳米线约瑟夫森结中的特征Andreev能级分裂，超过量子位能量，保护量子位免受对断裂激发。 我们计划通过传输来研究纳米线结，以确定开关电流及其栅极电压可调性。在微波频率和纳米线和量子电路的电压门控的潜力纳米线结的基本方面将得到解决。结合传输和微波实验需要一个混合电路布局，可移动的传输偏置电极嵌入在谐振电路。基于传输和传输实验的结果，将开发量子比特设计。在项目的最后阶段，将对纳米线transmon量子比特进行光谱研究，并确定相干性。

The goal of the proposed project is the experimental realization of an electrically-controlled transmon quantum bit (qubit). The quantum bit circuit will be based on superconductor/semiconductor nanowire Josephson junctions, where the critical current is controlled by a bottom gate or alternatively by a side gate electrode. Thus, the gate-controlled nanowire-based junction will serve as field tunable non-linear inductance in the qubit circuit. As for the nanowires, either bulk InAs nanowires or GaAs/InAs core/shell nanowires will be employed. The latter structure would provide an additional in-plane flux control. The characteristic Andreev level splitting in the nanowire Josephson junction, exceeding the qubit energy, protects the qubit from pair breaking excitations. We plan to investigate the nanowire junctions by transport to determine the switching current and its gate voltage tunability. Fundamental aspects of nanowire junctions at microwave frequencies and the potential of nanowires and voltage gating for quantum circuits will be addressed. Combining transport and microwave experiments requires a hybrid circuit layout with removable transport bias electrode embedded in a resonant circuit. Based upon the results from transport and transmission experiments a quantum bit design will be developed. At the final stage of the project, spectroscopic studies of the nanowire transmon qubit will be performed and the coherence will be determined.