One-kilometer quantum field breakthrough

The scheme of the experimental setup for the distribution of the orbital angular momentum in large volumes. Courtesy: CAO Juan

The team, led by Professor Guo Guangzang of the China University of Science and Technology (USTC) of the Chinese Academy of Sciences (CAS) and collaborators, was the first to realize the distribution of multidimensional entangled orbital angular momenta over a 1-km small-mode fiber. The result is published in Optica,

Increase channel capacity and noise immunity in quantum communications It is a strong practical motivation for encoding quantum information in multilevel systems, unlike qubits. From a fundamental point of view, entanglement in higher dimensions demonstrates more complex structures and stronger non-classical correlations. Multifaceted entanglement has demonstrated its potential to increase channel capacity and noise immunity in quantum information treatment. Despite these advantages, the distribution of multidimensional entanglement is relatively new and remains complex.

The orbital angular momentum of a photon is a multidimensional system that has received much attention in recent years. However, entanglement of the orbital angular momentum is subject to atmospheric turbulence or crosstalk in the mode and mode dispersion in optical fibers. It can transmit only a few meters and is limited by a two-dimensional distribution of entanglement.

In this work, the researchers reported the first distribution of three-dimensional entanglement of the orbital angular momentum (OAM) over a 1 km multimode optical fiber.

Using the method of active phase stabilization, they successfully transported through the fiber one photon from a three-dimensional pair of photons entangled in OAM. By their measures, they are able to certify three-dimensional entanglement through fidelity to the three-dimensional maximal entangled state (MES) 0.71 and violation of the Collins-Gizin-Linden-Massard-Popescu inequality (CGLMP).

In addition, they confirmed that multidimensional quantum entanglement undergoes transportation, violating Bell's generalized inequality, and violating ~ 3 standard deviations.

They showed that preservation of the wavefront is possible with precompensation, which could potentially provide further processing of information after the optical fiber. The developed method, in principle, can be expanded to higher OAM sizes and large distances.

Their work is a significant step forward in the dissemination of high obfuscation in transverse spatial modes of photons. In the future, they hope that, together with recent noise resistance results using higher dimensions, the work will motivate further experimental study into new protocols that include long distance quantum communications through fiber.

A new twist on quantum communication in fiber

Additional Information:
Huang Cao et al. Distribution of multidimensional entanglement of the orbital angular momentum over a 1 km long mode fiber, Optica (2020). DOI: 10.1364 / OPTICA.381403

One-kilometer breakthrough in a quantum field (2020, March 20)
retrieved March 21, 2020

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