We report on the experimental demonstration of high energy-time entanglement in two-photon states created in the process of spontaneous parametric down-conversion. We show that the classical variance product, which we violate by three orders of magnitude, actually represents a lower bound estimate of the number of information eigenmodes K. Explicit measurements estimate K to be greater than 100, with theoretical estimates predicting a value of as high as 1×106. These results provide incentive for the practical feasibility of large bandwidth quantum information processing, particularly in cryptography over large distances.
I. A. Khan and J. C. Howell, Experimental Demonstration of High Two-Photon Time-Energy Entanglement, Phys. Rev. A 73(3), 031801. https://doi.org/10.1103/PhysRevA.73.031801
American Physical Society