  We propose a mechanism to interface a transmission line resonator (TLR) with
a nano-mechanical resonator (NAMR) by commonly coupling them to a charge qubit,
a Cooper pair box with a controllable gate voltage. Integrated in this quantum
transducer or simple quantum network, the charge qubit plays the role of a
controllable quantum node coherently exchanging quantum information between the
TLR and NAMR. With such an interface, a maser-like process is predicted to
create a quasi-classical state of the NAMR by controlling a single-mode
classical current in the TLR. Alternatively, a "Cooper pair" coherent output
through the transmission line can be driven by a single-mode classical
oscillation of the NAMR.
