Wang Ji-Yin, Schrade Constantin, Levajac Vukan, van Driel David, Li Kongyi, Gazibegovic Sasa, Badawy Ghada, Op Het Veld Roy L M, Lee Joon Sue, Pendharkar Mihir, Dempsey Connor P, Palmstrøm Chris J, Bakkers Erik P A M, Fu Liang, Kouwenhoven Leo P, Shen Jie
QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands.
Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Sci Adv. 2022 Apr 22;8(16):eabm9896. doi: 10.1126/sciadv.abm9896.
We study a Cooper pair transistor realized by two Josephson weak links that enclose a superconducting island in an InSb-Al hybrid nanowire. When the nanowire is subject to a magnetic field, isolated subgap levels arise in the superconducting island and, because of the Coulomb blockade, mediate a supercurrent by coherent cotunneling of Cooper pairs. We show that the supercurrent resulting from such cotunneling events exhibits, for low to moderate magnetic fields, a phase offset that discriminates even and odd charge ground states on the superconducting island. Notably, this phase offset persists when a subgap state approaches zero energy and, based on theoretical considerations, permits parity measurements of subgap states by supercurrent interferometry. Such supercurrent parity measurements could, in a series of experiments, provide an alternative approach for manipulating and protecting quantum information stored in the isolated subgap levels of superconducting islands.
我们研究了一种由两个约瑟夫森弱链接实现的库珀对晶体管，这两个弱链接在锑化铟 - 铝混合纳米线中包围着一个超导岛。当纳米线受到磁场作用时，超导岛内会出现孤立的亚能隙能级，并且由于库仑阻塞，通过库珀对的相干共隧穿介导超电流。我们表明，对于低到中等磁场，这种共隧穿事件产生的超电流表现出一个相位偏移，该偏移区分超导岛上的偶数和奇数电荷基态。值得注意的是，当一个亚能隙态接近零能量时，这个相位偏移仍然存在，并且基于理论考虑，通过超电流干涉测量允许对亚能隙态进行宇称测量。在一系列实验中，这种超电流宇称测量可以为操纵和保护存储在超导岛孤立亚能隙能级中的量子信息提供一种替代方法。
