Post-selection free spatial Bell state generation

TL;DR

This paper introduces an experimental method to generate maximally entangled spatial photon pairs without post-selection, enabling high-brightness sources crucial for advanced free-space quantum communication.

Contribution

The method allows for the creation of high-brightness, maximally entangled spatial photon pairs without post-selection, improving efficiency over existing techniques.

Findings

Achieved maximally entangled spatial photon pairs without post-selection.

Enabled use of the full photon flux from the nonlinear crystal.

Provided a practical tool for high-brightness quantum communication sources.

Abstract

Spatial states of single photons and spatially entangled photon pairs are becoming an important resource in quantum communication. This additional degree of freedom provides an almost unlimited information capacity, making the development of high-quality sources of spatial entanglement a well-motivated research direction. We report an experimental method for generation of photon pairs in a maximally entangled spatial state. In contrast to existing techniques the method does not require post-selection and allows one to use the full photon flux from the nonlinear crystal, providing a tool for creating high-brightness sources of pure spatially entangled photons. Such sources are a prerequisite for emerging applications in free-space quantum communication.