  Atom arrays are a new type of quantum light-matter interface. Here, we
propose to employ one-dimensional ordered arrays as atomic waveguides. These
arrays support optical guided modes that do not decay into free space. We show
that these modes can be harnessed to mediate tunable, long-range interactions
between additional "impurity qubits" coupled to the chain, without need for
photonic structures. The efficient coupling between qubits and atomic
waveguides enables the realization of tunable qubit-qubit interactions, which
can be short- or long-range, dissipative or coherent, as well as chiral.
Moreover, owing to the two-level nature of atoms, these waveguides are
intrinsically quantum. In contrast to classical waveguides, where photons do
not interact with each other, atomic waveguides display strong non-linearities,
which create a tunable dissipative channel for qubit-qubit interactions, and
opens the door to the exploration of many-body physics between guided photons.
This physics is universal as it only relies on photon interference and can also
be observed with other types of quantum emitters, such as those in molecular or
solid-state systems.
