  The storage and retrieval of photonic quantum states, quantum memory, is a
key resource for a wide range of quantum applications. Here we investigate the
sensitivity of $\Lambda$-type quantum memory to experimental fluctuations and
drift. We use a variance-based approach, focusing on the effects of
fluctuations and drift on memory efficiency. We consider shot-to-shot
fluctuations of the memory parameters, and separately we consider longer
timescale drift of the control field parameters. We find the parameters that a
quantum memory is most sensitive to depend on the quantum memory protocol being
employed, where the observed sensitivity agrees with physical interpretation of
the protocols. We also present a general framework that is applicable to other
figures of merit beyond memory efficiency. These results have practical
ramifications for quantum memory experiments.
