  In this work we show that a tunable coupling between microwave resonators can
be engineered by means of simple Josephson junctions circuits, such as dc- and
rf-SQUIDs. We show that by controlling the time dependence of the coupling it
is possible to switch on and off and modulate the cross-talk, boost the
interaction towards the ultrastrong regime, as well as to engineer red and blue
sideband couplings, nonlinear photon hopping and classical gauge fields. We
discuss how these dynamically tunable superconducting circuits enable key
applications in the fields of all optical quantum computing, continuous
variable quantum information and quantum simulation - all within the reach of
state of the art in circuit-QED experiments.
