Shaikhaidarov Rais S, Kim Kyung Ho, Dunstan Jacob, Antonov Ilya, Golubev Dmitry, Antonov Vladimir N, Astafiev Oleg V
Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.
National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK.
Nat Commun. 2024 Oct 29;15(1):9326. doi: 10.1038/s41467-024-53600-y.
Synchronization of Bloch oscillations in small Josephson junctions (JJs) under microwave radiation, which leads to current quantization, has been proposed as an effect that is dual to the appearance of Shapiro steps. This current quantization was recently demonstrated in superconducting nanowires in a compact high-impedance environment. Direct observation of current quantization in JJs would confirm the synchronization of Bloch oscillations with microwaves and help with the realisation of the metrological current standard. Here, we place JJs in a high-impedance environment and demonstrate dual Shapiro steps for frequencies up to 24 GHz (I = 7.7 nA). Current quantization exists, however, only in a narrow range of JJ parameters. We carry out a systematic study to explain this by invoking the model of a JJ in the presence of thermal noise. The findings are important for fundamental physics and application in quantum metrology.
在微波辐射下，小约瑟夫森结（JJs）中布洛赫振荡的同步会导致电流量子化，这一效应被认为与夏皮罗台阶的出现是对偶的。最近在紧凑的高阻抗环境中的超导纳米线中证实了这种电流量子化。在约瑟夫森结中直接观察到电流量子化将证实布洛赫振荡与微波的同步，并有助于实现计量电流标准。在这里，我们将约瑟夫森结置于高阻抗环境中，并展示了高达24 GHz（I = 7.7 nA）频率下的对偶夏皮罗台阶。然而，电流量子化仅存在于约瑟夫森结参数的狭窄范围内。我们通过引入存在热噪声时约瑟夫森结的模型进行了系统研究来解释这一现象。这些发现对于基础物理学和量子计量学中的应用具有重要意义。
