Soviet Journal of Low Temperature Physics

Photoinduced macroscopic quantum tunneling in superconducting systems

A. A. Golub

Published Jun 1, 1985• 0 citations

Abstract

The problem of macroscopic quantum coherence in superconducting systems is studied theoretically. A two-level model of a SQUID with phonon-field coupling is considered. The probability of a transition, induced by a periodic perturbation, occurring between the lowest states of the two-well potential, describing the phase dependence of the energy in the SQUID, is calculated for a particular region of this coupling. Use is made of the conformity between this model and the resonance-level model. We also consider the strong-viscosity limit. It is shown that in this case the two-level model cannot be used to describe quantum interferometers.

DOI: 10.1063/10.0031304

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Soviet Journal of Low Temperature Physics

Photoinduced macroscopic quantum tunneling in superconducting systems

A. A. Golub

Published Jun 1, 1985• 0 citations

Publisher

Abstract

DOI: 10.1063/10.0031304

Related papers

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arXiv:1410.4388Oct 16, 20140 citations

{e}^{2}

. .AE

{T}_{cr}

the thermal fluctuations of the Josephson phase induce such a switching, and as

T<{T}_{cr}

the regime of the MQT occurs. In the absence of two-level systems (TLSs) a magnetic field applied parallel to the junction plane results in a smooth reduction of ${T}_{cr}(\mathrm{\ensuremath{\Phi}})$, where $\mathrm{\ensuremath{\Phi}}$ is an applied magnetic flux. As the TLSs are present in Josephson junctions we obtain a resonant enhancement of the MQT. This phenomenon manifests itself by a narrow peak in the dependence of ${T}_{cr}(\mathrm{\ensuremath{\Phi}})$ occurring in the intermediate range of $\mathrm{\ensuremath{\Phi}}$, i.e., $0<\mathrm{\ensuremath{\Phi}}<{\ensuremath{\phi}}_{0}$ (${\ensuremath{\phi}}_{0}$ is the magnetic flux quantum). We explain this effect quantitatively by a strong resonant suppression of the potential barrier for the Josephson phase escape that is due to the coherent quantum Rabi oscillations in two-level systems present in the junction.

\frac{h}{{e}^{2}}

T_{cr}

between the thermal fluctuation and quantum regimes of switching from the superconducting (the zero-voltage) state to a resistive one. In the absence of two-levels systems the crossover temperature shows a smooth decrease with an applied magnetic field characterized by an external flux

Φ

. Beyond that we predict a narrow peak in the dependence of

T_{cr}(Φ)

occurring in the intermediate range of

Φ

. The effect becomes more pronounced as the junction size increases. We explain this effect quantitatively by a strong resonant suppression of a potential barrier for the Josephson phase escape that is due to the coherent quantum Rabi oscillations in two-level systems present in the junction.