Arbitrarily loss-tolerant Einstein-Podolsky-Rosen steering allowing a demonstration over 1 km of optical fiber with no detection loophole

TL;DR

This paper presents a method for demonstrating EPR steering over 1 km of optical fiber with high loss, avoiding detection loopholes and enabling secure quantum communication over long distances.

Contribution

The authors develop arbitrarily loss-tolerant EPR steering tests that allow for loophole-free demonstrations over long fiber links, advancing quantum communication security.

Findings

Achieved a loophole-free EPR steering demonstration over 1 km fiber

Managed 87% total loss while maintaining detection loophole closure

Enabled secure quantum protocols over long-distance optical fibers

Abstract

Demonstrating nonclassical effects over longer and longer distances is essential for both quantum technology and fundamental science. The main challenge is loss of photons during propagation, because considering only those cases where photons are detected opens a "detection loophole" in security whenever parties or devices are untrusted. Einstein-Podolsky-Rosen (EPR) steering is equivalent to an entanglement-verification task in which one party (device) is untrusted. We derive arbitrarily loss-tolerant tests, enabling us to perform a detection-loophole-free demonstration of EPR-steering with parties separated by a coiled 1 km optical fiber, with a total loss of 8.9 dB (87%).