TY - JOUR

T1 - Squeezing of a quantum flux in a double rf-SQUID system

AU - Takashima, Kohji

AU - Matsuo, Shigemasa

AU - Fujii, Toshiyuki

AU - Hatakenaka, Noriyuki

AU - Kurihara, Susumu

AU - Zeilinger, Anton

PY - 2009

Y1 - 2009

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=77952477783&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77952477783&partnerID=8YFLogxK

U2 - 10.1088/1742-6596/150/5/052260

DO - 10.1088/1742-6596/150/5/052260

M3 - Article

AN - SCOPUS:77952477783

SN - 1742-6588

VL - 150

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

IS - 5

M1 - 052260

ER -