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

Kohji Takashima*, Shigemasa Matsuo, Toshiyuki Fujii, Noriyuki Hatakenaka, Susumu Kurihara, Anton Zeilinger

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)


    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
    Article number052260
    JournalJournal of Physics: Conference Series
    Issue number5
    Publication statusPublished - 2009

    ASJC Scopus subject areas

    • Physics and Astronomy(all)


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