Single-photon interference over 8.4 km urban atmosphere: towards testing quantum effects in curved spacetime with photons

TL;DR

This study demonstrates the feasibility of observing single-photon interference over 8.4 km in urban atmosphere, providing a practical approach to test quantum effects in curved spacetime and bridging quantum mechanics with general relativity.

Contribution

We designed and validated an unbalanced Michelson interferometer setup for long-distance single-photon interference experiments in free space.

Findings

Achieved phase measurement precision of 16.2 mrad.

Confirmed feasibility of testing quantum effects in curved spacetime over 8.4 km.

Demonstrated single-photon interference over a long-distance urban free-space channel.

Abstract

The emergence of quantum mechanics and general relativity has transformed our understanding of the natural world significantly. However, integrating these two theories presents immense challenges, and their interplay remains untested. Recent theoretical studies suggest that the single-photon interference covering huge space can effectively probe the interface between quantum mechanics and general relativity. We developed an alternative design using unbalanced Michelson interferometers to address this and validated its feasibility over an 8.4 km free-space channel. Using a high-brightness single-photon source based on quantum dots, we demonstrated single-photon interference along this long-distance baseline. We achieved a phase measurement precision of 16.2 mrad, which satisfied the measurement requirements for a gravitational redshift at the geosynchronous orbit by five times the standard deviation. Our results confirm the feasibility of the single-photon version of the Colella-Overhauser-Werner experiment for testing the quantum effects in curved spacetime.