**Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effect**

Recently we have proposed the method of Raman Adiabatic
Transfer of Optical States (RATOS) to manipulate the
optical state of light [1]. In this method a four-level atomic
medium in double-Lambda configuration is interacting with two pump
fields and a signal photon, which can be in a superposition of
two modes with different frequencies. Depending on the
intensity of the pump fields, only a particular superposition
will experience electromagnetically induced transparency and thus
can be slowed down. An adiabatic change in time of the pump fields can
then change this superposition dynamically.
Here we theoretically analyze the influence of an adiabatic change
in the spatial form of the pump fields. We demonstrate that the
signal photon then behaves like a charged quasi-particle: in
paraxial approximation its dynamics is governed by a Schroedinger-like
equation that includes a scalar and a vector quasi-potential whose
form is determined by the shape of the pump fields. We suggest
pump field configurations that generate potentials corresponding
to a constant electric and a constant magnetic quasi-field and show
that the magnetic quasi-field suppresses spatial dispersion
of the signal photon. Furthermore we devise a scheme of pump fields
that generates a vector potential of Aharonov-Bohm type.
This induces a topological phase shift on the signal field.
[1] J. Appel, K.-P. Marzlin and A.I. Lvovsky, Phys. Rev. A 73, 013804 (2006).