Stable entanglement in a quadripartite cavity optomechanics Fatemeh Mahmoudi Momenabadi, Hamid Reza Baghshahi, Mohammad Javad Faghihi and Sayyed Yahya Mirafzali Eur. Phys. J. Plus, 136 1 (2021) 7 Published online: 02 January 2021 DOI: 10.1140/epjp/s13360-020-00988-3