The effect of the voltage-dependent junction resistance R/sub j/ on the critical current decay of Josephson junctions was studied. In the thermal regime, the author has obtained a simple expression for the lifetime of the zero-voltage state which takes into account the nonlinear dependence of R/sub j/ on the voltage, removing an assumption of the resistivity shunted junction model (RSJ), which assumes an ohmic shunt resistance to describe the junction dissipation. These results are confirmed by experimental data which also show the relevance of the intrinsic dissipation due to the presence of quasiparticles. This latter aspect is relevant, because it allows extremely underdamped systems to be obtained at low temperatures. These conditions are particularly interesting to study a macroscopic quantum aspect, namely the effects of the presence of quantized energy levels on the supercurrent decay. The dependence of this latter effect on the junction resistance is also briefly discussed.The effect of the voltage-dependent junction resistance R/sub j/ on the critical current decay of Josephson junctions was studied. In the thermal regime, the author has obtained a simple expression for the lifetime of the zero-voltage state which takes into account the nonlinear dependence of R/sub j/ on the voltage, removing an assumption of the resistivity shunted junction model (RSJ), which assumes an ohmic shunt resistance to describe the junction dissipation. These results are confirmed by experimental data which also show the relevance of the intrinsic dissipation due to the presence of quasiparticles. This latter aspect is relevant, because it allows extremely underdamped systems to be obtained at low temperatures. These conditions are particularly interesting to study a macroscopic quantum aspect, namely the effects of the presence of quantized energy levels on the supercurrent decay. The dependence of this latter effect on the junction resistance is also briefly discussed.

IEEE Transactions on MagneticsMar 1, 19910 citations

Macroscopic Quantum Effects in the Current-Biased Josephson Junction

Michel Devoret, Daniel ESTEVE, C. Urbina +3 more

Modern problems in condensed matter sciencesJan 1, 19929 citations

Supercurrent decay in extremely underdamped Josephson junctions

B. Ruggiero, C. Granata, Vittorio Giulio Palmieri +3 more

We present an experimental study of the effective dissipation relevant in the thermally activated supercurrent decay of extremely underdamped Josephson junctions. Data referring to the supercurrent decay of ${\mathrm{N}\mathrm{b}/\mathrm{A}\mathrm{l}\mathrm{O}}_{x}/\mathrm{Nb}$ Josephson junctions are compared with the Kramers theory. Our measurements allow us to obtain the ``effective'' resistance to be used in the resistively shunted junction model that results to be the subgap resistance due to the presence of thermally activated quasiparticles. The extremely low dissipation level obtained at low temperatures renders our result quite interesting in view of experiments in the quantum limit.We present an experimental study of the effective dissipation relevant in the thermally activated supercurrent decay of extremely underdamped Josephson junctions. Data referring to the supercurrent decay of ${\mathrm{N}\mathrm{b}/\mathrm{A}\mathrm{l}\mathrm{O}}_{x}/\mathrm{Nb}$ Josephson junctions are compared with the Kramers theory. Our measurements allow us to obtain the ``effective'' resistance to be used in the resistively shunted junction model that results to be the subgap resistance due to the presence of thermally activated quasiparticles. The extremely low dissipation level obtained at low temperatures renders our result quite interesting in view of experiments in the quantum limit.

Physical review. B, Condensed matterJan 1, 199832 citations

Extremely underdamped Josephson junctions for low noise applications

B. Ruggiero, C. Granata, E. Esposito +2 more

We present a design of extremely underdamped Josephson junctions either for use in experiments in the quantum limit or for devices using the switching dynamics of the junction, when a low noise level is mandatory. High resistance molybdenum meander lines integrated with the junction allow one to increase the insulation of the sample from its electromagnetic environment. We report an experimental study of the effective dissipation relevant in the thermally activated supercurrent decay presenting evidence of a substantial reduction of the dissipation level at low temperature.We present a design of extremely underdamped Josephson junctions either for use in experiments in the quantum limit or for devices using the switching dynamics of the junction, when a low noise level is mandatory. High resistance molybdenum meander lines integrated with the junction allow one to increase the insulation of the sample from its electromagnetic environment. We report an experimental study of the effective dissipation relevant in the thermally activated supercurrent decay presenting evidence of a substantial reduction of the dissipation level at low temperature.

Applied Physics LettersJul 5, 199916 citations

{\mathrm{N}\mathrm{b}/\mathrm{A}\mathrm{l}\mathrm{O}}_{x}/\mathrm{Nb}

Josephson junctions are compared with the Kramers theory. Our measurements allow us to obtain the ``effective'' resistance to be used in the resistively shunted junction model that results to be the subgap resistance due to the presence of thermally activated quasiparticles. The extremely low dissipation level obtained at low temperatures renders our result quite interesting in view of experiments in the quantum limit.