Squeezing of Josephson phases in d.c. superconducting quantum interferencedevices

We theoretically study the two-mode squeezing of Josephson phases in d.c, s uperconducting interference devices. The non-linearity of phase interaction s required for the squeezing is mediated by the external electromagnetic fi elds. Since the squeezing is one quantum aspect based on the Heisenberg unc ertainty relation, the Josephson phase squeezing provides another scheme fo r investigating the quantum nature of macroscopic objects. The squeezing of the Josephson phases can be observed by detecting the quantum fluctuation of the supercurrent through the Josephson current-phase relation. (C) 1998 Elsevier Science Ltd. All rights reserved.