  We propose an in-situ tunable chiral quantum system, composed of a quantum
emitter coupled to a waveguide based on the Rice-Mele model (where we alternate
both the on-site potentials and tunnel couplings between sites in the waveguide
array). Specifically, we show that the chirality of photonic bound state, that
emerges in the bandgap of the waveguide, depends only on the energy of the
qubit; a parameter that is easy to tune in many artificial atoms. In contrast
to previous proposals that have either shown imperfect chirality or fixed
directionality, our waveguide QED scheme achieves both perfect chirality and
the capability to switch the directionality on demand with just one tunable
element in the device. We also show that our model is easy to implement in both
state-of-the-art superconducting circuit and quantum dot architectures. The
results show technological promise in creating long-range couplers between
qubits while maintaining, in principle, zero crosstalk.
