  We calculate the integrated-pulse quantum efficiency of single-photon sources
in the cavity quantum electrodynamics (QED) strong-coupling regime. An
analytical expression for the quantum efficiency is obtained in the
Weisskopf-Wigner approximation. Optimal conditions for a high quantum
efficiency and a temporally localized photon emission rate are examined. We
show the condition under which the earlier result of Law and Kimble [J. Mod.
Opt. 44, 2067 (1997)] can be used as the first approximation to our result.
