Optimizing inhomogeneous spin ensembles for quantum memory

We propose a general method to maximize the fidelity of writing, storage and reading of quantum information (QI) in a spectrally inhomogeneous spin ensemble used as quantum memory. The method is based on preselecting the optimal spectral portion of the ensemble by a judiciously designed pulse. It allows drastic improvement of quantum memory realized by spin ensembles that store QI from a resonator or an optical beam.