  Both cavity QED and photons are promising candidates for quantum information
processing. We consider a combination of both candidates with a single photon
going through spatially separate cavities to entangle the atomic qubits, based
on the input-output process of the cavities. We present a general expression
for the input-output process regarding the low-Q cavity confining a single
atom, which works in a wide range of parameters. Focusing on low-Q cavity case,
we propose some schemes for quantum information processing with Faraday
rotation using single photons, which is much different from the high-Q cavity
and strong coupling cases.
