### Abstract

We investigate the nonstationary boundary effect for a quantum flux in a double rf-SQUID system. In a superconducting ring interrupted by a dc-SQUID (so-called double rf-SQUID), the Josephson potential can be controlled by the magnetic flux through the dc-SQUID ring. This system is equivalent to an anharmonic oscillator with a time-dependent frequency. A rapid change of the magnetic flux in the dc-SQUID leads to the nonadiabatic mixing of the quantum states for a quantum flux in a double rf-SQUID. Therefore, this becomes a circuit analogue of the dynamical Casimir effect in quantum field theory. We perform numerical calculations for the quantum state evolution of the quantum flux within a harmonic approximation, taking account of the nonadiabatic effect. We found that the resulting state distribution has a super-Poissonian character that reflects flux squeezing caused by the Bogoliubov transformation between eigenstates at different times.

Original language | English |
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Article number | 052260 |

Journal | Journal of Physics: Conference Series |

Volume | 150 |

Issue number | 5 |

DOIs | |

Publication status | Published - 2009 |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*Journal of Physics: Conference Series*,

*150*(5), [052260]. https://doi.org/10.1088/1742-6596/150/5/052260