Towards cascaded chiral interfaces for superconducting qubits

Unidirectional light-matter interactions enable the creation of cascaded quantum systems, with prospective applications in driven-dissipative entanglement generation, study of quantum many-body physics, and operations on itinerant photons. While unidirectional, or chiral, interfaces between superconducting qubits and photons has been previously demonstrated, hardware overhead and photon loss currently limit extending these approaches to multi-qubit experiments. Here, we present experimental results demonstrating a chiral qubit platform, in which an array of transmon qubits can be unidirectionally coupled to a metamaterial waveguide. In our scheme, each qubit is tunably coupled to the waveguide at spatially separated points using parametric couplers. We discuss the merits and limitations of this architecture for cascading an array of qubits and avenues for improvements in future experiments.