  We propose a scheme for continuous-variable quantum cloning of coherent
states with phase-conjugate input modes using linear optics. The quantum
cloning machine yields $M$ identical optimal clones from $N$ replicas of a
coherent state and $N$ its replicas of phase conjugate. This scheme can be
straightforwardly implemented with the setup accessible at present since its
optical implementation only employs simple linear optical elements and homodyne
detection. Compared with the original scheme for continuous variables quantum
cloning with phase-conjugate input modes proposed by Cerf and Iblisdir [Phys.
Rev. Lett. 87, 247903 (2001)], which utilized a nondegenerate optical
parametric amplifier, our scheme loses the output of phase-conjugate clones and
is regarded as irreversible quantum cloning.
