Curator's Take
This article marks the first experimental realization of a cascaded chiral network built from superconducting qubits, demonstrating that directional, low‑loss coupling can be achieved over distances up to half a metre and used to stabilize reconfigurable multipartite entanglement. By exploiting the shared waveguide as a dissipative resource, the team observes photon‑number–dependent time sorting—a clear signature of strong photon‑photon interactions that are inaccessible in reciprocal baths—opening a new platform for many‑body quantum optics and modular quantum‑processor architectures. While still limited to four emitters, the work provides a concrete pathway toward scalable, nonreciprocal quantum hardware for both simulation of exotic light‑matter phases and distributed quantum information processing.
— Mark Eatherly
Summary
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.