Seminarium Optyczne

Entanglement is a resource that enables quantum information processing operations, such as secure communication or quantum teleportation. Pairs of entangled photons are ideally suited for distributing entanglement, but the sources that generate them do so unreliably. Sources often generate the wrong number of photon pairs, which leads to failed quantum operations.Reliable sources can be made through use of entanglement swapping. Starting with two entangled pairs (four photons total), swapping is accomplished by taking one photon from each pair and fusing them together into a single "herald" photon. Measurement of the herald photon generates an electrical signal which certifies that the process was successful and that exactly one pair of entangled photons has been produced. The swapping process erases information in the quantum state about the frequency-content of the fused photons, preserving the superposition state of the remaining photon pair. Photon pairs produced in this way are ideally-suited for reliable entanglement distribution