Robust entanglement between a movable mirror and a cavity field system with an optical parametric amplifier Xianwu Mi, Jiangxiang Bai and Song Ke-hui Eur. Phys. J. D, 67 6 (2013) 115 Published online: 25 June 2013 DOI: 10.1140/epjd/e2013-30659-7