  We put forward two efficient entanglement concentration protocols (ECPs) for
distilling the maximally entangled NOON state from arbitrary less-entangled
NOON state with only an auxiliary single photon. With the help of the weak
cross-Kerr nonlinearities, both the two ECPs can be used repeatedly to get a
high success probability. In the first ECP, the auxiliary single photon should
be shared by the two parties say Alice and Bob. In the second ECP, the
auxiliary single photon is only possessed by Bob, which can greatly increase
the practical success probability by avoiding the transmission loss. Moreover,
Bob can operate the whole protocol alone, which makes the protocol more simple.
Therefore, our two ECPs, especially the second ECP may be more useful and
convenient in the current quantum information processing.
