We propose a scheme to implement the $\overrightarrow{1}2$ universal quantum cloning machine of Buzek and Hillery [Phys. Rev. A $54,$ 1844 (1996)] in the context of cavity QED. The scheme requires cavity-assisted collision processes between atoms, which cross through nonresonant cavity fields in the vacuum states. The cavity fields are only virtually excited to face the decoherence problem. That’s why the requirements on the cavity quality factor can be loosened.

• Received 15 July 2002

DOI:https://doi.org/10.1103/PhysRevA.67.024304