  Stroboscopic spin flips have already been shown to prolong the coherence
times of quantum systems under noisy environments. Uhrig's dynamical decoupling
scheme provides an optimal sequence for a quantum system interacting with a
dephasing bath. Several experimental demonstrations have already verified the
efficiency of such dynamical decoupling schemes in preserving single qubit
coherences. In this work we describe the experimental study of Uhrig's
dynamical decoupling in preserving two-qubit entangled states using an ensemble
of spin-1/2 nuclear pairs in solution state. We find that the performance of
odd-order Uhrig sequences in preserving entanglement is superior to both
even-order Uhrig sequences and periodic spin-flip sequences. We also find that
there exists an optimal length of the Uhrig sequence at which the decoherence
time gets boosted from a few seconds to about 30 seconds.
