Complete experimental toolbox for alignment-free quantum communication

TL;DR

This paper presents a comprehensive experimental toolkit for alignment-free quantum communication using rotationally invariant photonic states, enabling resource-efficient quantum key distribution and entanglement distribution without shared reference frames.

Contribution

It introduces a complete set of methods for encoding and decoding quantum information in rotationally invariant states, facilitating alignment-free quantum communication.

Findings

Successful demonstration of alignment-free quantum key distribution

Proof-of-principle entanglement distribution without shared reference frames

Violation of Bell inequality in an alignment-free setup

Abstract

Quantum communication employs the counter-intuitive features of quantum physics to perform tasks that are im- possible in the classical world. It is crucial for testing the foundations of quantum theory and promises to rev- olutionize our information and communication technolo- gies. However, for two or more parties to execute even the simplest quantum transmission, they must establish, and maintain, a shared reference frame. This introduces a considerable overhead in communication resources, par- ticularly if the parties are in motion or rotating relative to each other. We experimentally demonstrate how to circumvent this problem with the efficient transmission of quantum information encoded in rotationally invariant states of single photons. By developing a complete toolbox for the efficient encoding and decoding of quantum infor- mation in such photonic qubits, we demonstrate the fea- sibility of alignment-free quantum key-distribution, and perform a proof-of-principle alignment-free entanglement distribution and violation of a Bell inequality. Our scheme should find applications in fundamental tests of quantum mechanics and satellite-based quantum communication.