# Direct transfer of pump amplitude to parametric down-converted photons

## TL;DR

This study demonstrates that the transverse amplitude of photons generated by spontaneous parametric down-conversion closely follows that of the pump beam, with implications for quantum imaging and communication.

## Contribution

It provides the first detailed numerical and experimental analysis of how pump amplitude transfers to down-converted photons and how aperture size affects the Fourier image plane.

## Key findings

- Photon amplitude transfer from pump to SPDC confirmed
- Fourier image plane shifts with aperture size
- Implications for quantum imaging and communication

## Abstract

We numerically and experimentally show that all photons generated by spontaneous parametric down-conversion (SPDC) follow a transverse amplitude similar to that of the pump. This amplitude transfer from pump to SPDC is revealed in the Fourier image plane of the down-converted photons restricted by an aperture. We also observe a considerable shift of the image plane from the actual Fourier plane, when size of the aperture is gradually increased. The shift of the Fourier image of down-converted photons affects the quality of spatial mode-based projection in various quantum correlation experiments with parametric down-converted photon pairs. The results may be useful in applications of down-converted photons for quantum imaging and quantum communication.