State independent QKD

TL;DR

This paper introduces an adaptive, alignment-free method for quantum non-locality experiments and quantum key distribution that operates without prior knowledge of the shared quantum state or additional alignment tools.

Contribution

The authors develop a novel adaptive procedure enabling alignment in quantum experiments and QKD without prior state knowledge or extra measurement devices.

Findings

Successful implementation in fiber-based QKD with polarization-entangled photons

Procedure operates without additional alignment tools or prior state information

Enhances robustness and simplifies quantum communication setups

Abstract

We present an adaptive procedure for aligning quantum non-locality experiments without any knowledge of the two-qudit state shared by the participating parties. The quantum state produced by the source, its unitary evolution as well as the actual measurement bases remain unknown to both parties at all times. The entanglement of the quantum state helps establish desired correlations between individual measurement bases of the two distant parties. We implement the procedure in a fiber-based quantum key distribution (QKD) setup with polarization-entangled photons, where we do not rely on any additional alignment tools such as lasers or polarizers. In a QKD scenario the procedure can be done without any additional measurements as those that are performed regardless.