Novel macroscopic quantum effects due to interactions between intrinsic Josephson junctions

本征约瑟夫森结(IJJ)系统是超导层和绝缘层在原子尺度上堆叠的系统，作为未来量子信息处理技术的可能候选者，受到了广泛的关注。在这项研究中，我们研究了对IJJ系统至关重要的层间耦合效应对量子比特操作的基本现象，如宏观量子隧穿(MQT)态中的非能级量子化(ELQ)。我们观察到，在微波辐射下，ELQ开关电流概率分布的分离随着温度的升高而不同。我们还发现，跨到MQT区域的温度强烈地依赖于IJJ的结几何。最后，我们成功地制作了一个小结数小于10个结的IJJ器件，这对于理解层间耦合效应是非常有用的。

Intrinsic Josephson junction(IJJ) systems, where the superconducting layer and the insulating layer are stacked in an atomic scale, is extensively attracted as a possible candidate of future quantum information processing technology. In this study, we investigate the interlayer coupling effects, which are essentially important for the IJJ systems, to fundamental phenomena of quantum bits operation, such as anenergy level quantization(ELQ) in macroscopic quantum tunneling(MQT) state. We observed that the separation of the switching current probability distribution attributed to ELQ under microwave irradiation is variedwith increasing temperatures. We also found that a crossover temperature to MQT regime is strongly dependent on the junction geometry of IJJs. Finally, we succeeded in fabricating an IJJ device with small junction numbers below 10 junctions, which is quite useful for the understanding of the interlayer coupling effects.