  Means to coherently control single x-ray photons in resonant scattering of
light off nuclei by electric or magnetic fields are investigated theoretically.
In order to derive the time response in nuclear forward scattering, we adapt
the Maxwell-Bloch equations known from quantum optics to describe the resonant
light pulse propagation through a nuclear medium. Two types of time-dependent
perturbations of nuclear forward scattering are considered for coherent control
of the resonantly scattered x-ray quanta. First, the simultaneous coherent
propagation of two pulses through the nuclear sample is addressed. We find that
the signal of a weak pulse can be enhanced or suppressed by a stronger pulse
simultaneously propagating through the sample in counter-propagating geometry.
Second, the effect of a time-dependent hyperfine splitting is investigated and
we put forward a scheme that allows parts of the spectrum to be shifted forward
in time. This is the inverse effect of coherent photon storage and may become a
valuable technique if single x-ray photon wavepackets are to become the
information carriers in future photonic circuits.
