Squeezing of a quantum flux in a double rf-SQUID system

Kohji Takashima (Corresponding author), Shigemasa Matsuo, Toshiyuki Fujii, Noriyuki Hatakenaka, Susumu Kurihara, Anton Zeilinger

Publications: Contribution to bookContribution to proceedings


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 languageEnglish
Title of host publication25th International Conference on Low Temperature Physics (LT25)
PublisherIOP Publishing Ltd
Number of pages4
Publication statusPublished - 2009

Publication series

SeriesJournal of Physics: Conference Series

Austrian Fields of Science 2012

  • 103026 Quantum optics
  • 103025 Quantum mechanics

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