The superconducting proximity effect in semiconductor nanowires has recently enabled the study of new superconducting architectures, such as gate-tunable superconducting qubits and multiterminal Josephson junctions. As opposed to their metallic counterparts, the electron density in semiconductor nanosystems is tunable by external electrostatic gates, providing a highly scalable and in situ variation of the device properties. In addition, semiconductors with large g-factor and spin–orbit coupling have been shown to give rise to exotic phenomena in superconductivity, such as φ₀ Josephson junctions and the emergence of Majorana bound states. Here, we report microwave spectroscopy measurements that directly reveal the presence of Andreev bound states (ABS) in ballistic semiconductor channels. We show that the measured ABS spectra are the result of transport channels with gate-tunable, high transmission probabilities up to 0.9, which is required for gate-tunable Andreev qubits and beneficial for braiding schemes of Majorana states. For the first time, we detect excitations of a spin-split pair of ABS and observe symmetry-broken ABS, a direct consequence of the spin–orbit coupling in the semiconductor.

中文翻译：

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弹道半导体约瑟夫森结中具旋转性安德列夫键态的微波光谱

半导体纳米线中的超导邻近效应最近使人们能够研究新的超导架构，例如门可调超导量子位和多端约瑟夫森结。与它们的金属对应物相反，半导体纳米系统中的电子密度可以通过外部静电门来调节，从而提供了器件特性的高度可扩展和原位变化。此外，具有大半导体克α-因子和自旋-轨道耦合已经显示出产生在超导奇异的现象，如φ ₀约瑟夫森交界处和马约拉纳约束州的出现。在这里，我们报告的微波光谱测量直接揭示了弹道半导体通道中安德列夫键合态（ABS）的存在。我们表明，所测得的ABS光谱是具有可调门的传输通道的结果，传输概率高达0.9，这是可调门的Andreev量子位所必需的，并且对马里亚纳邦的编织方案有益。第一次，我们检测了自旋分裂对的ABS的激发，并观察到对称断裂的ABS，这是半导体中自旋-轨道耦合的直接结果。