  We present a system which allows to tune the coupling between a
superconducting resonator and a transmission line. This storage resonator is
addressed through a second, coupling resonator, which is frequency-tunable and
controlled by a magnetic flux applied to a superconducting quantum interference
device (SQUID). We experimentally demonstrate that the lifetime of the storage
resonator can be tuned by more than three orders of magnitude. A field can be
stored for 18 {\mu}s when the coupling resonator is tuned off resonance and it
can be released in 14 ns when the coupling resonator is tuned on resonance. The
device allows capture, storage, and on-demand release of microwaves at a
tunable rate.
