YQI Talk - Frank Yang - CalTech

Title: Many-body light–matter physics in a chiral quantum network Chiral light-matter interaction describes coupling between atoms and photons that depends on the propagation direction of light. Unidirectional coupling of multiple qubits to a photonic bath produces a cascaded quantum system, where ordered, long-range interactions and the absence of information backflow produce a unique setting for quantum networking and studies of fundamental quantum optics. In this talk, I will present our experimental results on such a cascaded system, where we have realized an array of superconducting qubits with unidirectional strong coupling to a metamaterial waveguide. Each individual qubit is parametrically coupled to two spatially separated points of the waveguide, enabling chirality by interference of two emission pathways. We cascade four chiral qubits across two modules connected by a half-meter cable, allowing us to access many-body regimes of light-matter physics. Using the shared waveguide bath, we dissipatively stabilize four-qubit entangled states with a reconfigurable structure and demonstrate genuine multipartite entanglement, a regime that is inaccessible in the absence of chirality. We then probe the chain with weak pulses, observing temporal sorting of scattered radiation into photon bound states, a signature of strong photon-photon interactions. Together, these results demonstrate the utility of cascaded quantum systems for many-body quantum optics. Livestream the Event Here! (Yale Login Required)