  We propose a scheme for single-atom, quantum control of the direction of
propagation of a coherent field incident, via a tapered fiber, upon a
microtoroidal whispering-gallery-mode (WGM) resonator. The scheme involves
overcoupling of the fiber-taper to the resonator and strong coupling of an atom
to the evanescent field of the WGM, i.e., an atom-field coupling that exceeds
the total WGM linewidth. In contrast to previous, related schemes that operate
in the bad-cavity regime, the proposed scheme can operate effectively with much
stronger incident fields, while also preserving their coherent nature. It can
also serve to prepare an entangled state of the atom and coherent optical
pulses propagating in opposite directions along the fiber. We evaluate the
fidelity of preparation of such a state taking into account absorption and
atomic spontaneous emission and demonstrate that high fidelities should be
possible with realistic parameters.
