# Extending Wheeler's delayed-choice experiment to Space

## TL;DR

This paper extends Wheeler's delayed-choice experiment to space by implementing a satellite-ground interferometer over thousands of kilometers, confirming quantum predictions at an unprecedented scale and demonstrating the wave-particle duality in space-based quantum systems.

## Contribution

It introduces a space-based realization of Wheeler's delayed-choice experiment using satellite-ground interferometry, expanding quantum tests to a new large-scale environment.

## Key findings

- Confirmed quantum mechanical predictions at a space scale
- Demonstrated wave-particle duality with satellite-reflected photons
- Showed feasibility of space-based quantum experiments involving multiple photon degrees of freedom

## Abstract

Gedankenexperiments have consistently played a major role in the development of quantum theory. A paradigmatic example is Wheeler's delayed-choice experiment, a wave-particle duality test that cannot be fully understood using only classical concepts. Here, we implement Wheeler's idea along a satellite-ground interferometer which extends for thousands of kilometers in Space. We exploit temporal and polarization degrees of freedom of photons reflected by a fast moving satellite equipped with retro-reflecting mirrors. We observed the complementary wave-like or particle-like behaviors at the ground station by choosing the measurement apparatus while the photons are propagating from the satellite to the ground. Our results confirm quantum mechanical predictions, demonstrating the need of the dual wave-particle interpretation, at this unprecedented scale. Our work paves the way for novel applications of quantum mechanics in Space links involving multiple photon degrees of freedom.