  We propose a dynamical approach to quantum memories using a synchronous
oscillator-cavity model, in which the coupling is shaped in time to provide the
optimum interface to a symmetric input pulse. This overcomes the known
difficulties of achieving high quantum input-output fidelity with storage times
long compared to the input signal duration. Our generic model is applicable to
any linear storage medium ranging from a superconducting device to an atomic
medium. We show that with temporal modulation of coupling and/or detuning, it
is possible to mode-match to time-symmetric pulses that have identical pulse
shapes on input and output.
