Reshared post from +EuroTech
Teleportation Across Ocean Waters
by , ; Germany
The University of Vienna and the Austrian Academy of Science are the new record holders in quantum teleportation distances: they have teleported a photon over 143 kilometers, breaking the record set by the former Chinese teleportation team. But what makes this teleportation so special is the underlying communication technology, which is fundamentally different from the fiber-optic approach of the Chinese experiment: they used wireless communication and attenuation to transmit signals through the atmosphere under less-than-optimal conditions.
The team has successfully teleported photos between two Canary Islands, La Palma and Tenerife. This was no relaxing vacation experiment: They had to overcome a significant challenge to accomplish this feat. The photons had to be sent through the turbulent atmosphere. Optical fibers were not an alternative, as signal loss would be too severe for distances over 143 km.
They sent two data sets from one island to the other, namely information about the quantum states, and the same information in conventional form. The data is then combined with a battery of synchronization algorithms, and the result used to recreate the quantum state. Xiao-song Ma explained the technical details behind the innovation in their solution: “An important step for our successful teleportation was a method known as ‘active feed-forward’, which we have used for the first time in a long-distance experiment. It helped us to double the transfer rate.” On the receiver end, the signals are combined on using a frequency-uncorellated polarization-entangled photon pair source, ultra-low-noise single-photon detectors and entanglement-assisted clock synchronization.
The next step is to use low-orbital satellites – which fly between 200 and 1200 km above Earth’s surface – to transport signals. Rupert Ursin explains, “Our latest results are very encouraging with a view to future experiments in which we either exchange signals between Earth and satellites or send messages from one satellite to another. On the way through the atmosphere from La Palma to Tenerife, our signals have been attenuated by a factor of roughly one thousand. Nevertheless, we managed to perform a quantum teleportation experiment. In satellite-based experiments, the distances to be travelled are longer, but the signal will have to pass through less atmosphere. We have now created a sound basis for such experiments.”
And after that? They want to teleport across the world. Anton Zeilinger elaborates, “The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale… The goal is to launch a ‘quantum satellite mission’.” Welcome to the future: one with a global quantum Internet.
Security in the quantum Internet
A worldwide information network enhanced with quantum technology means that quantum mechanics must play a key role in secure message exchange. Cracking conventional cyphers with quantum technology is trivial: you have more or less unlimited parallelisation possibilities within each single computation, meaning that cracking a typical secure key can be done with very little effort. To defeat a hacker equipped with a quantum computer, you need more difficult cryptography algorithms specially designed for a quantum computer.
Forget the beaming, Scotty – give me a secure Internet connection instead!
Official press release: http://medienportal.univie.ac.at/presse/aktuelle-pressemeldungen/detailansicht/artikel/quantum-physics-at-a-distance/
Full article: http://www.nature.com/nature/journal/v489/n7415/full/nature11472.html
Picture: © Institute for Quantum Optics and Quantum Information (IQOQI)
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