Many-body quantum optics in a cascaded chiral network

Chiral quantum emitters interact with light only in one propagation direction, allowing them to be linked into cascaded systems in which photons mediate ordered, long-range interactions. Such systems are predicted to host novel regimes of many-body physics of light and matter. Exploring these regimes requires arrays of identical quantum emitters with directional, low-loss coupling to guided photons, a combination that has thus far remained experimentally out of reach. Here we realize a cascaded network of superconducting qubits using an architecture that overcomes these bottlenecks. We implement a four-qubit chain spanning two modules, with separations ranging from millimeters to half a meter, and exploit the shared waveguide as a dissipative resource to stabilize reconfigurable entanglement, reaching a genuinely multipartite regime unavailable in reciprocal baths. By scattering weak pulses off the chain, we observe photons sorted in time by photon number, a signature of the strong photon-photon interactions mediated by the emitters. Together, these results provide experimental access to many-body light-matter regimes that are beyond the reach of reciprocal systems.