  We describe a new kind of phase-preserving quantum amplifier which utilizes
dissipative interactions in a parametrically-coupled three-mode bosonic system.
The use of dissipative interactions provides a fundamental advantage over
standard cavity-based parametric amplifiers: large photon number gains are
possible with quantum-limited added noise, with no limitation on the
gain-bandwidth product. We show that the scheme is simple enough to be
implemented both in optomechanical systems and in superconducting microwave
circuits.
