  The full control of single photons is important in quantum information and
quantum networking. A convenient storage device for photons is the key to
memory assisted quantum communication and computing. While even a simple
optical fiber can act as a convenient and reliable storage device, its storage
time is tightly fixed and cannot be adapted. Therefore, the photon storage
should ideally be actively controllable by external means, such as magnetic or
electric control fields. In order to multiplex several photons, an active
routing would also be desirable. Here we show that single photons of a
semiconductor quantum dot can be deliberately delayed by an atomic vapor. Also,
the output path can be selected, depending on an external magnetic field. By
selecting the input polarization of the photons and by aligning the external
magnetic field of the hot atomic vapor, the delay-based storage can be fine
tuned to a deliberate value. With an overall delay of 25 ns, we are able to
fine tune by more than 600 ps. Depending on the input polarization, the photons
are routed into different output ports. The experimental data is fully
resembled by a theoretical model, which describes the group velocity delay
under consideration of spectral diffusion and considers the complex refractive
index of the atomic vapor. The present results enable the use of an atomic
vapor as a wavelength selective delay and allows for routing the single photons
according to their polarization and an external magnetic field.
