Minimum Number of Copies in the Measurement of Multi-Photon Entanglement

Multi-photon entanglement has been successfully made by experimental groups. As the increase of photon number, several problems are encountered, say, greater number of copies, longer time, the error of fidelity and so on. In this paper, we present a new scheme based on Lagrange multiplier and feedback to save the measure copies in multi-photon experiment and five percent of measuring time, also guarantee the acceptable error of fidelity. All the results have been supported by the data of eight photon experiment. Furthermore, same approach is applied in the simulation for ten photon entanglement, and 22.45 percent of copies are saved, optimized copy distribution gives better estimation of fidelity than the average copy distribution.