Squeezing Between Charge and Phase Fluctuations in Small Josephson Junctions.

De-Xin Miao, Juju Hu, Yinghua Ji +1 more

A. Tagliacozzo

Y. Harada, Hideaki Takayanagi, A. A. Odintsov

We investigate Cooper-pair tunneling in a circuit consisting of two dc-superconducting quantum interference devices in series, with a gate capacitively coupled to the central island. Measurements cover a wide range of values of the ratio between Josephson coupling energy ${E}_{J}$ and charging energy ${E}_{C}$. The $\frac{{E}_{J}}{{E}_{C}}$ ratio dependence of the supercurrent is well described by the orthodox theory provided that strong fluctuations of the Josephson phase due to the electromagnetic environment are taken into account. Our data can be interpreted in terms of squeezing of the charge fluctuations with decreasing $\frac{{E}_{J}}{{E}_{C}}$ ratio.

Wang Wenguo, MANFRED L. RISTIG

Yanling Li

The quantization scheme of the mesoscopic mutual inductance circuit with super- conducting Josephson junctions is given.By means of squeezing unitary transformation,the energy level and the ground state vector of the system are obtained.Then,the quantum fluctuations of excess charges and phase difference between the sides of Josephson junction in the ground state are investigated.It is found that the ground state of the system is a rotated two single-mode squeezed vacuum state.

Cyrus F. Hirjibehedin, Steven J. Weber, Gabriel Samach +8 more