Probabilistic cloning of a single-atom state via cavity QED

We propose a scheme for probabilistically cloning a two-level state of an atom to a polarization photon via cavity QED system combined with linear optics elements. By choosing appropriate parameters, a controlled phase flip (CPF) gate between the atom and the probe photon is realized. Then we can judge that the cloning process should be continued (with the optimal probability) or interrupted by detecting the probe photon. If the cloning can be continued, the original atom state is deterministically cloned to the cloning photon by performing two more CPF gates and three single-qubit unitary operations. Otherwise, if the detection shows that the cloning should be interrupted, the cloning photon and the relevant operations are omitted.