Hyper-entagled quantum communication tested in the open air
Particles entangled by the rules of quantum physics are distinguished by the fact that they share a plurality of properties with each other and each measurement on one of the particles immediately determines the state of the other particle. While in the past experiments on entanglement were mostly focused on one of these properties, the extension of the study to several properties would have great advantages for quantum communications because it would significantly increase speed and efficiency of the information transmission.
This approach has therefore been extensively pursued in quantum research for a long time. However, it has a weakness: the so-called “hyperentanglement” – the entanglement of particles over several properties – so far could only be demonstrated in laboratory experiments. For connections over longer distances, transmission through the air would be essential. However, this could be distorted by turbulences in the atmosphere, so the concerns in quantum physics.
A research team of the Vienna Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences (ÖAW) around research group leader Rupert Ursin could now invalidate these concerns. As reported in a new publication in the journal “Nature Communications”, they were able to transfer and measure quantum information through the airspace on the basis of two properties of entangled light particles. These properties were the direction of oscillation and the time of production.
The Hedy Lamarr telescope on the roof of the Austrian Academy of Sciences in Vienna and a receiver station at the University of Natural Resources and Applied Life Sciences, Vienna, successfully demonstrated these two properties of entangled light particles despite atmospheric turbulences along the transmission route. “Experiments with entanglements of time-related parameters have so far only been successful in glass fibers. In addition to the frequently investigated direction of vibration of the particles, we were now able to transfer the time of particle production as an additional property of the particles across the air,” said Fabian Steinlechner and Sebastian Ecker, authors of the experiment.
ÖAW researcher Rupert Ursin explained the significance of this first-time investigation of the “hyperentanglement” in the atmosphere for the further development of quantum communication: “Hyperentanglement allows light particles, information encoded in different properties, to be exchanged at the same time. This could significantly speed up the speed of data transmission in quantum communication. ” The reason: The entanglement of multiple properties can drastically reduce the number of particles required for the transmission of information. This makes the quantum connections faster and more efficient.
More information: https://www.oeaw.ac.at/pr
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