Tunable directional photon scattering from a pair of superconducting qubits

The two frequency-modulated superconducting qubits act as a trembling mirror for microwave photons with on-demand tunable directionality. The ability to control the direction of scattered light is crucial to provide flexibility and scalability for a wide range of on-chip applications, such as integrated photonics, quantum information processing, and nonlinear optics. Tunable directionality can be achieved by applying external magnetic fields that modify optical selection rules, by using nonlinear effects, or interactions with vibrations. However, these approaches are less suitable to control microwave photon propagation inside integrated superconducting quantum devices. Here, we demonstrate on-demand tunable directional scattering based on two periodically modulated transmon qubits coupled to a transmission line at a fixed distance. By changing the relative phase between the modulation tones, we realize unidirectional forward or backward photon scattering. Such an in-situ switchable mirror represents a versatile tool for intra- and inter-chip microwave photonic processors. In the future, a lattice of qubits can be used to realize topological circuits that exhibit strong nonreciprocity or chirality.

Automated summary

The two frequency-modulated superconducting qubits act as a switchable mirror for microwave photons, providing on-demand tunable directional scattering. This ability is crucial for various on-chip applications, such as integrated photonics, quantum information processing, and nonlinear optics. By changing the relative phase between the modulation tones, unidirectional forward or backward photon scattering can be realized. This in-situ switchable mirror represents a versatile tool for intra- and inter-chip microwave photonic processors.