Study on the Quantum Current-Mirror Effect

在这项研究中所研究的效应是在两个小约瑟夫森结阵列之间精确的电流复制。这种效应的基础是所谓的单电荷隧穿现象。因此，在这种现象中，期望两个阵列中的库珀对隧道的相关性。在本次研究期间，我们取得了以下成果：1。我们成功地制造了基于电流镜效应的电流倍增器。从实际应用的角度阐明了该倍频器的特性，如电路连接方式、偏置电压范围及其与器件精度的关系。当前倍频器的实现是本研究的主要目标之一。阐明了该效应的几个特征，如每个结的约瑟夫森耦合能与最大可重复电流之间的关系、构成具有镜像效应的电流反射器件的阵列中结的数目的关系、镜像效应的偏置电压范围等。在三阵列器件中，我们观察到没有通过耦合电容直接连接的阵列之间的电流存在重复。这是一个出乎意料的惊人现象。这意味着这种效应是由于不同阵列中的库珀对隧道的非局部相关而不是它们的局部相关。最后一点对这一效应产生了新的兴趣，这需要对小约瑟夫森结的物理学有更深刻的认识。因此，需要从新的角度进行更多的研究来充分理解这一效应。

The effect studied in this research is a precise electric current duplication between in two arrays of small Josephson junctions. The basis of this effect is the so called single-charge tunneling phenomenon. Therefore, correlation of Cooper-pair tunneling in the two arrays is expected in this phenomenon. In the period of this research, we have made the following achievements.1.We have succeeded in making a current doubler based on the current-mirror effect. Characteristics of the doubler device have been clarified from a practical point of view, such as circuit connection scheme, bias voltage range and its relation to the accuracy of the device. This realization of a current doubler is one of the main targets of this research.2.Several features of this effect has been clarified such as the relation between the Josephson coupling energy of each junction to the maximum duplicable current, the relation of the number of the junctions in the array which composes the current-mirror device with the mirror effect, bias voltage range for the mirror effect, etc.3.In a three-array device, we have observed a duplication of the current between arrays which are not directly connected through coupling capacitances. This is a remarkable phenomenon which has not been expected. And this implies that the effect is due to a nonlocal correlation of the Cooper-pair tunnelings in the different arrays rather than a local correlation of them.The final point brings a new interest on this effect and it will require more profound insight on the physics of small Josephson junction. So more works from new viewpoints are needed to understand this effect sufficiently.