Swept bias experiments carried out on Josephson junctions yield the distributions of the probabilities of early switching from the zero voltage state. Kramers theory of thermally activated escape from a one-dimensional potential is well known to fall
short of explaining such experiments when the junctions are at millikelvin temperatures. We propose a simple revision of the theory which is shown to yield extremely good agreement with experimental data.
We have developed a model for experiments in which the bias current applied to a Josephson junction is slowly increased from zero until the junction switches from its superconducting zero-voltage state, and the bias value at which this occurs is reco
rded. Repetition of such measurements yields experimentally determined probability distributions for the bias current at the moment of escape. Our model provides an explanation for available data on the temperature dependence of these escape peaks. When applied microwaves are included we observe an additional peak in the escape distributions and demonstrate that this peak matches experimental observations. The results suggest that experimentally observed switching distributions, with and without applied microwaves, can be understood within classical mechanics and may not exhibit phenomena that demand an exclusively quantum mechanical interpretation.
We revisit the interpretation of earlier low temperature experiments on Josephson junctions under the influence of applied microwaves. It was claimed that these experiments unambiguously established a quantum phenomenology with discrete levels in sha
llow wells of the washboard potential, and macroscopic quantum tunneling. We here apply the previously developed classical theory to a direct comparison with the original experimental observations, and we show that the experimental data can be accurately represented classically. Thus, our analysis questions the necessity of the earlier quantum mechanical interpretation.
An electrical circuit consisting of two capacitively coupled inductive loops, each interrupted by a Josephson junction, is analyzed through the classical RSCJ model. The same circuit has recently been studied experimentally and the results were used
to demonstrate quantum mechanical entanglement in the system by observing the correlated states of the two inductive loops after initial microwave perturbations. Our classical analysis shows that the observed phenomenon exists entirely within the classical RSCJ model, and we provide a detailed intuitive description of the transient dynamics responsible for the observations.
