Tunable quantum switcher and router of single atoms using localized artificial magnetic fields

We propose to generate localized artificial magnetic fields using two thin Raman laser beams intersected at a narrow region of a two-leg ladder, where the frequency difference must approximately match the energy offset between the two legs. Based on this method, we investigate the single-atom transport in a two-leg ladder with only two rungs, which, together with the legs, enclose a localized artificial magnetic flux. Here, the atoms on the two legs (channels) possess different onsite energies that produce another energy offset. We find that the atom incoming from the left channel can experience from blockade to transparency via modifying the onsite energy, tunneling strength, or magnetic flux, which can be potentially used for a quantum switcher. Furthermore, the atom incoming from the left channel can also be perfectly routed into the right leg, when, intriguingly, the outgoing atom in the right channel possesses a quasimomentum that can be modulated by the magnetic flux. The result may be potentially used for the interface that controls the communication between two individual quantum devices of cold atoms. The method can also be generalized to other artificial quantum systems, such as superconducting quantum circuit systems, optical systems, etc.