  The M{\o}lmer-S{\o}rensen gate is a state-of-the-art entangling gate in the
ion trap quantum computing where the gate fidelity can exceed 99\%. Here we
propose an analogous implementation in the setting of cavity QED. The cavity
photon mode acts as the bosonic degree of freedom in the gate in contrast of
that played by a phonon mode in ion traps. This is made possible by utilising
cavity assisted Raman transitions interconnecting the logical qubit states
embedded in a four-level energy structure, making the "anti-Jaynes-Cummings"
(AJC) term available under the rotating-wave approximation. We identify
practical sources of infidelity and discuss their effects on the gate
performance. Our proposal not only demonstrates an alternative entangling gate
scheme but also sheds new light on the relationship between ion traps and
cavity QED, in the sense that many techniques developed in the former are
transferable to the latter through our framework.
