Fundamental Limits on Polarization Entanglement Distribution in Optical Fiber

TL;DR

This paper establishes fundamental limits on distributing polarization entanglement over optical fibers, providing bounds on achievable rates and benchmarks for quantum communication without repeaters, considering realistic fiber effects and detector imperfections.

Contribution

We introduce a channel model for polarization entanglement distribution in optical fibers and derive capacity bounds, offering a rigorous benchmark for long-distance quantum communication.

Findings

Derived bounds on entanglement distribution rates in optical fibers.

Identified optimal repeaterless performance limits for realistic fibers.

Showed robustness of bounds under detector dark counts.

Abstract

Characterizing the ultimate rates of entanglement distribution is essential for both foundational research and the practical deployment of quantum technologies. To investigate these limits, we introduce an erasure-Pauli channel model describing the distribution of polarization entanglement in optical fiber. For this channel, we derive bounds on the rates of entanglement distribution and related quantum resources under optimal local operations and two-way classical communication (two-way assisted capacities). This framework allows us to determine the optimal repeaterless performance achievable over realistic optical fibers affected by polarization mode dispersion, thereby providing a rigorous benchmark for long-distance polarization-based quantum communication. Finally, we show that both our model and capacity bounds remain robust under the inclusion of detector dark counts.