The comparison between the local and nonlocal entangled wavelength to time mapping

Abstract

The dispersive wavelength to time mapping with the entangled photon source is an effective way of measuring the spectral information of the entangled photon pairs. This approach avoids the usage of spectral filtering equipment like the monochromator, which reduces the measuring time and the system's complexity. The wavelength-to-time mapping method can be divided into local mapping and nonlocal mapping depending on whether the measurement utilizes the frequency correlation of the entangled photon pairs. For local mapping, the spectral information of signal photons is directly mapped to the time domain through dispersion without utilizing the frequency correlation between the photon pair. For nonlocal mapping, the signal photons with spectral information are directly detected. And the corresponding idler photons are dispersed. With the help of the frequency correlation between the photon pair, the spectral information on signal photons can be recorded in count measurement. In this letter, the two types of mapping results are theoretically and experimentally compared. The theoretical result indicates that the two types of mapping results are the same when the pump light of the entangled source is ideal monochromatic with infinite linewidth. However, when using a real pump light with finite linewidth, the theoretical and experimental result of the two types of mapping is different. The difference in the result indicates the potential influence of the mapping method, which can further help to select a more suitable mapping method for different measuring conditions.