Nonlinear optics provides the fundamental processes that enable the generation, manipulation, and detection of quantum states of light. Among these processes, frequency conversion plays a central role because it allows quantum information encoded in photons to be transferred between different spectral regions without loss of coherence [1-2]. The NZI Quantum project aims to demonstrate single-photon frequency conversion at telecom wavelengths by exploiting the exceptional nonlinear properties of near-zero-index (NZI) conductive-oxide thin films.

In conventional media, frequency conversion at the single-photon level requires high pump intensities and long interaction lengths, which severely limit integration and scalability. NZI materials, characterised by an extremely small refractive index and a giant effective nonlinear response, provide a new route to achieving strong nonlinear coupling within deeply sub-wavelength volumes and at significantly lower power levels [3-6]. By optically pumping these materials close to their zero-index regime, it becomes possible to tailor the local electromagnetic density of states and to enhance light–matter interaction far beyond what is accessible in standard dielectrics or semiconductors.

The project will experimentally investigate this mechanism using thin NZI films integrated on planar substrates and will develop a quantum-optical model describing the conversion dynamics under realistic non-perturbative conditions. Emphasis will be placed on quantifying conversion efficiency, spectral tunability, and noise suppression at the single-photon level. The combination of experimental demonstration and theoretical modelling will establish clear performance benchmarks for NZI-based quantum frequency converters and define the material and design parameters required for scalable implementation.

By integrating advanced material growth, ultrafast optical characterisation, and quantum-optical detection, NZI Quantum will lay the groundwork for a new class of compact, energy-efficient quantum photonic interfaces that can bridge different communication bands. The resulting technology would directly impact the development of large-scale quantum communication networks and quantum processors by enabling seamless spectral connectivity between otherwise incompatible components.