In Xu and Kuang (\textit{ J. Phys. A: Math. Gen.} 39 (2006) L191), the authors claim that, for single-mode excited entangled coherent states $| \Psi_{ \pm}(\alpha,m)>$, \textquotedblleft the photon excitations lead to the decrease of the concurrence in the strong field regime of $| \alpha | ^{ 2}$ and the concurrence tends to zero when $| \alpha | ^{ 2}\to \infty$". This is wrong.
Categories: quant-ph