  Single-photon coherent optics represents a fundamental importance for the
investigation of quantum light-matter interactions. While most work has
considered the interaction in the steady-state regime, here we demonstrate that
a single-photon pulse shorter than any relaxation time in a medium propagates
without energy loss and is consistently transformed into a zero-area pulse. A
general analytical solution is found for photon passage through a cold ensemble
of $\Lambda$-type atoms confined inside a hollow core of a single-mode
photonic-crystal fiber. We use the robust far off-resonant Raman scheme to
control the pulse reshaping by an intense control laser beam and show that in
the case of cw control field, for exact two-photon resonance, the outgoing
photon displays an oscillating temporal distribution, which is the quantum
counterpart of a classical field ringing, while for nonzero two-photon detuning
a slow photon is produced. We demonstrate also that a train of readout control
pulses coherently recalls the stored photon in many well-separated temporal
modes, thus producing time-bin entangled single-photon states. Such states,
which allow sharing quantum information among many users, are highly demanded
for applications in long-distance quantum communication.
