Events at Physics |
Josephson Parametric Amplifiers (JPAs) can perform quantum-limited
readout of superconducting qubits. However, since they are
reflection-based amplifiers, an external RF circulator is always
necessary to suppress back-action. A new approach is to use directional
parametric amplification by driving multiple parametric processes
simultaneously with different pump phases. SQUID and SLUG amplifiers in
fact operate by a similar mechanism: the interference between parametric
processes driven by internal oscillations at the Josephson frequency
suppresses the reverse gain and explains the high level of isolation in
this devices. In this talk I am going to discuss a general approach to
the study of parametric devices driven by multiple pump signals. As
opposed to traditional JPAs, where only two modes, signal and idler,
interact, in multi-pump devices three or more modes are pumped
simultaneously. I will show how to use directed graphs to compute the
scattering properties of such multi-mode devices and design parametric
nonreciprocal components, including circulators and directional amplifiers.