Quantum Tomography of Inductively-Created Large Multiphoton States

Abstract: The generation of quantum entangled states of many particles is a central goal of quantum information science. Characterizing such states is a complex task that demands exponentially large resources as particles are being added. Previously, we demonstrated a resource efficient source that can generate, in principal, entanglement between any number of photons. This source recursively fuse photon pairs generated by a pulsed laser into a multiphoton entangled state. In the current work, we perform quantum state tomography on the photon pair source and quantum process tomography on the fusion operation. As a result, the full quantum Greenberger-Horne-Zeilinger (GHZ) state of any number of photons can be calculated. We explore the prospects of our scheme and calculate nonlocality and genuine \textit{N}-photon entanglement thresholds for states with up to twelve photons.