Visualizing the Hardy's Paradox using Hyper‐Entanglement‐Assisted Ghost Imaging

Abstract The concept of quantum nonlocality, lying at the heart of quantum information science and technologies, is physically counter‐intuitive and mathematically elusive. Here, a hyper‐entanglement‐assisted ghost imaging system is designed to visualize the evidence of Hardy's paradox by capturing the purely nonlocal photonic events with a spatially resolved intensified charge‐coupled device (ICCD) camera. In the two‐photon polarization‐spatial‐mode hyper‐entangled state, spatial entanglement conveys the ghost images while polarization entanglement encodes the imaging channels in the logical structure of Hardy's nonlocality proof. Then whether the single ghost image of a skull‐shape object is observed or not can be a direct yet intuitive signature to support or defy quantum mechanics. Moreover, the degree of the violation of locality can be characterized by the contrast‐to‐noise ratio of ghost images macroscopically, and the nonlocal behavior of violating the locality microscopically at the single‐pixel level with a reasonable confidence level of 75% is also achieved. The proposed strategy not only sheds new light on the fundamental issue of quantum mechanics, but also holds promise for developing hyper‐entanglement‐based quantum imaging technology.