  We investigate the possibility of exploiting the speed and low noise features
of Josephson junctions for detecting sinusoidal signals masked by Gaussian
noise. We show that the escape time from the static locked state of a Josephson
junction is very sensitive to a small periodic signal embedded in the noise,
and therefore the analysis of the escape times can be employed to reveal the
presence of the sinusoidal component. We propose and characterize two detection
strategies: in the first the initial phase is supposedly unknown (incoherent
strategy), while in the second the signal phase remains unknown but is fixed
(coherent strategy). Our proposals are both suboptimal, with the linear filter
being the optimal detection strategy, but they present some remarkable
features, such as resonant activation, that make detection through Josephson
junctions appealing in some special cases.
