Decoherence protection for nuclear spin quantum memory in a quantum dot

We reconsider the possibility of storing quantum information in an ensemble of nuclear spins constituting a semiconductor quantum dot. The nuclear magnetic moments are collectively interacting with an excess electron of the quantum dot through inhomogeneous hyperfine coupling. We present a configuration in which the collective nuclear spin states used as the qubit basis are energetically separated from the remaining states, thus protecting the quantum memory from various sources of decoherence