  Dissipation even at zero temperature reduces quantum fluctuations and tends
to localize particles. A notable exception is the nonlinear dissipation due to
quasiparticle tunneling in a Josephson junction. It is well known that
quasiparticle dissipation does not prevent the phase particle in a
superconducting junction to coherently tunnel to the next-nearest minimum even
though tunneling to the nearest minimum is suppressed. The reason is that the
dissipative action admits an instanton solution, the so-called Korshunov
instanton. Here, we analyze this model at elevated bias current $I$. We find
that besides the known regime where the logarithm of the tunneling rate scales
as $I^{2/3}$ there is novel regime with a scaling $I^2$. We argue that the
novel regime opens an opportunity for an experimental verification of the
Korshunov instantons as the elevated bias current leads to a larger tunneling
rate compared to earlier results.
