In our digital future, how will we keep our information private? A new breakthrough in quantum communications may help — it could lead to a more secure internet.
Felix Bussieres and his co-authors, physicists based in Geneva, have helped quantum teleportation clear some of the technical hurdles to its broader application. These applications include secure communication channels.
Quantum teleportation involves transferring the quantum state of one particle to another particle over some distance. Teleportation is based on the quantum phenomenon of entanglement. When two particles are entangled, they share some of their basic quantum properties on a fundamental level — doing something to one particle will automatically have an effect on the other particle.
What makes entanglement weird is that the particles will still have this relationship even if they are moved far apart from each other. Albert Einstein famously described this behaviour as “spooky action at a distance.”
This may sound crazy, but this entanglement allows for teleportation — movement of information directly from one place to another. Physicists take a pair of entangled particles, separate them, and then use the “spooky action” to move quantum information from one particle to the other.
The most exciting applications of teleportation and entanglement are in quantum cryptography and quantum computing.
Quantum cryptography uses this transfer of quantum information to allow secure communication. The security of conventional cryptography, a cornerstone of the internet, is based on the difficulty of certain mathematical problems. Should there be a way to efficiently solve those problems, these communications would no longer be secure. Due to the delicate nature of entanglement, quantum cryptography is much more secure — any attempts to listen in on a secure conversation would be detected.
Quantum computing allows researchers to use the properties of entanglement and quantum information to solve certain types of problems vastly more quickly than is possible on a conventional computer. Some of the problems that quantum computers are very good at solving include those that encrypt internet communications. Possible future quantum computers could thus undermine the security of our communications.
Teleportation over FiOS
The big new development in this paper, posted on January 27 on the scientific preprint repository arXiv.org, is that the researchers have put together two important pieces needed to apply this phenomenon in large-scale networks. They were able to teleport quantum information over standard fibre optic cable (currently used for internet communications) into a quantum memory device.
Being able to transmit entangled photons over fibre optic cables is a key step to more broadly viable quantum networks, as it allows the use of existing communications infrastructure.
One big problem left to solve was how to get stored quantum information from the special memory devices used in this experiment to communicate with fibre optic cables.
The issue is that fibre optic cable works best with light that falls in a fairly restricted set of wavelengths. Unfortunately, the light wavelengths that work well for fibre optic transmission are different from those needed for the quantum memory storage.
The researchers found a way to put these two components together. Using cleverly designed optical systems, pairs of entangled photons could be made so that one particle in the pair could easily travel over fibre optic cable, and the other particle could easily be stored in the quantum memory.
The combination of these two pieces opens the door to making quantum routers and quantum signal boosters, allowing larger and more powerful quantum networks built on top of existing internet infrastructure.
Much work still needs to be done before quantum teleportation is possible outside of the lab — for example, the devices used to analyse the teleported information are based on superconducting wire cooled down to 2.5 degrees above absolute zero. But, this research brings us one step closer to the day when you can buy a super-secure quantum router at Amazon.
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