Photon Number Resolution via Multi-Photon Subtraction in a Waveguide-QED Setting

A description of states of light in terms of photons allows for a clear delineation between classical and non-classical light. The development of single-photon sources and detectors has enabled experimental studies of quantum light at the single-photon level, proving essential for applications in quantum communication, sensing, and imaging. Multi-photon quantum states, existing in higher-dimensional spaces, extend these applications and open opportunities to study the rich space of non-classical light states. Platforms for sourcing and characterizing such states have been increasingly explored to leverage the quantum resources they offer. Arithmetic operations of photon addition and subtraction, allow for generating non-classical multi-photon light from classical sources like coherent and squeezed states, as well as for photon-number-resolved (PNR) detection. PNR detection is essential for characterizing multi-photon states,providing access to their photon-number distributions and higher-order correlations, and enabling advanced quantum tomography.