  Hybrid systems consisting of different types of qubits are promising for
building quantum computers if they combine useful properties of their
constituent qubits. However, they also pose additional challenges if one type
of qubits is more susceptible to environmental noise than the others. Dynamical
decoupling can help to protect such systems by reducing the decoherence due to
the environmental noise, but the protection must be designed such that it does
not interfere with the control fields driving the logical operations. Here, we
test such a protection scheme on a quantum register consisting of the
electronic and nuclear spins of a nitrogen-vacancy center in diamond. The
results show that processing is compatible with protection: The dephasing time
was extended almost to the limit given by the longitudinal relaxation time of
the electron spin.
