  The behaviour of quantum open systems, and their output response, when driven
by quantum input noise in a nonclassical state is of key importance to quantum
technology. Here we give explicit constructions of quantum modulating filters
which generate desired nonclassical states (coherent states, cat states, shaped
single and multi-photon states) of quantum optical fields from vacuum noise
input. The nonclassical state features (coherence, entanglement, Fock state,
etc.) of the modulating filter, itself a linear passive open system, are
transferred to the continuous variable output field state. The filter dynamics
may additionally shape the output to obtain specific target states. It is shown
that the open dynamics of a general quantum Markov system driven by these
nonclassical inputs is equivalent to the cascaded filter-plus-system model with
vacuum field inputs.
