Quantum mechanics

Quantum decoherence

Quantum key distribution

Materials science

Optical fiber

Computer science

Statistical physics

Photon

Physics

Multi-mode optical fiber

Photon entanglement

Quantum entanglement

Optics

Quantum information science

Single-mode optical fiber

Quantum

Composite material

Fiber

Human–computer interaction

Mode (computer interface)

Science Advances

The global quantum network requires the distribution of entangled states over long distances, with substantial advances already demonstrated using polarization. While Hilbert spaces with higher dimensionality, e.g., spatial modes of light, allow higher information capacity per photon, such spatial mode entanglement transport requires custom multimode fiber and is limited by decoherence-induced mode coupling. Here, we circumvent this by transporting multidimensional entangled states down conventional single-mode fiber (SMF). By entangling the spin-orbit degrees of freedom of a biphoton pair, passing the polarization (spin) photon down the SMF while accessing multiple orbital angular momentum (orbital) subspaces with the other, we realize multidimensional entanglement transport. We show high-fidelity hybrid entanglement preservation down 250 m SMF across multiple 2 × 2 dimensions, confirmed by quantum state tomography, Bell violation measures, and a quantum eraser scheme. This work offers an alternative approach to spatial mode entanglement transport that facilitates deployment in legacy networks across conventional fiber.

Multidimensional entanglement transport through single-mode fiber