A new method of preparing a single photon in temporally delocalized entangled modes is proposed and analyzed. We
show that in a medium of four-level atoms with tripod-level configuration a strong parametric interaction between two
one-photon pulses emerges, if the medium was initially prepared in a coherent superposition of the two ground states,
while a strong classical field drives the neighbor transition from the third ground state. The analytical solution of
Maxwell equations reveals that under the electromagnetically induced transparency (EIT), the quantum fields propagate
with significantly small absorption and with different group velocities that leads to their temporal split into well-separated
pulses, the amplitudes of which are well controlled by the driving field. The proposed scheme can serve as a
robust source of narrow-band one-photon qubits with an entanglement between two temporal modes, not sensitive to
losses in atmosphere and in telecommunication waveguides. We show also that in our scheme a controllable degree of
temporal entanglement can be achieved.
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