  A Josephson tunnel junction transistor based on quasiparticle injection is
proposed. Its operation relies on the manipulation of the electron distribution
in one of the junction electrodes. This is accomplished by injecting
quasiparticle current through the junction electrode by two additional tunnel
coupled superconductors. Both large supercurrent enhancement and fast quenching
can be achieved with respect to equilibrium by varying quasiparticle injection
for proper temperature regimes and suitable superconductor combinations. Joined
with large power gain this makes the device attractive for applications where
reduced noise and low power dissipation are required.
