Few-mode-fiber technology fine-tunes losses of quantum communication systems

TL;DR

This paper presents a novel few-mode fiber approach using orbital angular momentum modes to transmit phase-encoded single-photon states over 500 meters, reducing losses and enhancing long-distance quantum communication feasibility.

Contribution

It introduces a new method combining time-bin encoding with few-mode fiber multiplexing to eliminate post-selection losses in quantum communication.

Findings

Successful transmission of phase-encoded single-photon states over 500 meters

Demonstration of loss-free quantum state transmission in few-mode fibers

Feasibility of long-distance quantum cryptography using the proposed scheme

Abstract

A natural choice for quantum communication is to use the relative phase between two paths of a single-photon for information encoding. This method was nevertheless quickly identified as impractical over long distances and thus a modification based on single-photon time-bins has then become widely adopted. It however, introduces a fundamental loss, which increases with the dimension and that limits its application over long distances. Here, we are able to solve this long-standing hurdle by employing a few-mode fiber space-division multiplexing platform working with orbital angular momentum modes. In our scheme, we maintain the practicability provided by the time-bin scheme, while the quantum states are transmitted through a few-mode fiber in a configuration that does not introduce post-selection losses. We experimentally demonstrate our proposal by successfully transmitting phase-encoded single-photon states for quantum cryptography over 500 m of few-mode fiber, showing the feasibility of our scheme.