Observation of Quantum Zeno blockade on Chip

When overlapping in an optical medium with nonlinear susceptibility, light waves can interact with each other, changing their phases, wavelengths, shapes, and so on. Such nonlinear effects, discovered over a half century ago, have given rise to a breadth of important applications. Applying to quantum-mechanical signals, however, they face fundamental challenges arising from the multimode nature of the interacting electromagnetic fields, such as phase noises and Raman scattering. Quantum Zeno blockade allows strong interaction of light waves without them physically overlapping, thus providing a viable solution for those challenges, as indicated in recent bulk-optics experiments. Here, we report on the observation of quantum Zeno blockade on chip, where a light wave is modulated by another in a distinct "interaction-free" manner. For quantum applications, we also verify its operations on a single-photon level. Our results promise a scalable platform for overcoming several grand challenges faced by nonlinear optics and quantum information processing, enabling, e.g., manipulation and interaction of quantum signals without decoherence.