  The hyperfine interaction with nuclear spins (or, Overhauser noise) has long
been viewed as a leading source of decoherence in individual quantum dot spin
qubits. Here we show that in a coupled multi-qubit system consisting of as few
as four spins, interactions with nuclear spins can have the opposite effect
where they instead preserve the collective quantum state of the system. This
noise-induced state preservation can be realized in a linear spin qubit array
using current technological capabilities. Our proposal requires no control over
the Overhauser fields in the array; only experimental control over the average
interqubit coupling between nearest neighbors is needed, and this is readily
achieved by tuning gate voltages. Our results illustrate how the role of the
environment can transform from harmful to helpful in the progression from
single-qubit to multi-qubit quantum systems.
