Orbital angular momentum entanglement over a 1 km few-mode fiber.

Schematic of the experimental setup for high-dimensional orbital angular momentum entanglement distribution. Credit: CAO Huan

A team from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) first realized distribution of high-dimensional orbital angular momentum entanglement over a 1 km few-mode fiber.

The orbital angular momentum (OAM) of photon is a high dimensional system which has been paid much attention to in recent years. However, orbital angular momentum entanglement is susceptible to atmospheric turbulence or mode crosstalk and mode dispersion in optical fibers. It can only transmit a few meters, and is limited to two-dimensional entanglement distribution.

The team reported the first distribution of three-dimensional orbital angular momentum entanglement via a 1-km-long few-mode optical fiber.

With their measures, they have been able to certify three-dimensional entanglement via a fidelity to the three-dimensional maximally entangled state (MES) of 0.71, and a violation of a Collins–Gisin–Linden–Massar–Popescu (CGLMP) inequality. They also certified that the high-dimensional quantum entanglement survives the transportation by violating a generalized Bell inequality, obtaining a violation of ~3 standard deviations.

Their work is a significant step forward for distributing high-dimensional entanglement in the transverse spatial modes of photons.

The result has been published in Optica. (Phys.org)

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