Steady state entanglement of two atoms created by classical driving field

The stabilization of entanglement[1-7] caused by action of a classical driving field in the system of two-level atoms with the dipole interaction accompanied by spontaneous emission is discussed. An exact solution shows that the maximum amount of concurrence that can be achieved in Lamb-Dicke limit is $0.43$. Dependence of entanglement on interatomic distance and classical driving field, beyond Lamb-Dicke limit, is examined numerically. [1] \"{O}. \c{C}ak{\i}r, A. Klyachko, and A. Shumovsky, quant-ph/0406081 [2] R. Tana\'{s} and Z. Ficek, J. Opt. B {\bf 6}, S610 (2004); quant-ph/0309195. [3] S.G. Clark and A.S. Parkins, Phys. Rev. A {\bf 90}, 047905 (2003 ). [4] B. Kraus and J.I. Cirac, Phys. Rev. Lett. {\bf 92}, 013602 (2004) . [5] S. Nicolosi, A. Napoli, A. Messina, F. Petruccione, Phys. Rev. A {\bf 70}, 022511 (2004). [6] J.B. Xu and S.B. Li, quant-ph/0401010. [7] M.A. Can, \"{O}. \c{C}ak{\i}r, A.A. Klyachko, and A.S. Shumovsky, Phys. Rev. A {\bf 68}, 022305 (2003).