**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. A four-level atomic medium in
double-$\Lambda$ configuration is interacting with two pump
fields and a signal photon with very slow group velocity.
An adiabatic change in time of the pump fields can then
generate a slow photon in a superposition of different frequencies.
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
Schr\"odinger-like equation that includes a scalar and a vector
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 field.
Furthermore we devise a scheme of pump fields that generates a vector
potential of Aharonov-Bohm type which induces a topological phase shift
for slow photons.