  Directional transport is obtained in various multimode systems by driving
multiple, nonreciprocally-interfering interactions between individual bosonic
modes. However, systems sustaining the required number of modes become
physically complex. In our microwave-optomechanical experiment, we show how to
configure nonreciprocal transport between frequency components of a single
superconducting cavity coupled to two drumhead oscillators. The frequency
components are promoted to Floquet modes and generate the missing dimension to
realize an isolator and a directional amplifier. A second cavity left free by
this arrangement is used to cool the mechanical oscillators and bring the
transduction noise close to the quantum limit. We furthermore uncover a new
type of instability specific to nonreciprocal coupling. Our approach is generic
and can greatly simplify quantum signal processing and the design of
topological lattices from low-dimensional systems.
