Scientists are moving closer to making super-secure and super-fast quantum internet possible: they are now able to “teleport” high-fidelity quantum information over a total distance of 44 kilometers (27 miles).
Data fidelity and transfer distance are crucial when it comes to building a real, functional quantum Internet, and making progress in any of these areas is a cause for celebration for those building our next generation communications network.
In this case, the team reached a level of fidelity (data accuracy) greater than 90 percent with its quantum information, in addition to sending it through extensive fiber optic networks similar to those that form the backbone of our existing Internet.
“We are excited about these results,” says physicist Panagiotis Spentzouris, from the Fermilab particle and accelerator physics laboratory at the California Institute of Technology (Caltech).
“This is an important achievement on the way to building technology that will redefine how we conduct global communication.”
Quantum internet technology uses qubits; unmeasured particles that remain suspended in a mixture of possible states, as revolving data yet to be established.
Qubits that are presented to each other have their identities “entangled” in ways that become obvious when they are finally measured. Imagine these entangled qubits as a pair of dice – although each can land on any number, it is guaranteed that both will add up to seven, no matter how far apart. Data in one location instantly reflects data in another.
Through an intelligent arrangement of three entangled qubits, it is possible to force the state of one particle to adopt the ‘dice roll’ of another through its mutually entangled partner. In quantum land, this is as good as turning one particle into another, teleporting your identity across a blink of an eye.
The entanglement still needs to be established at the beginning, and then maintained as the qubits are sent to their final destination via optical fibers (or satellites).
The unstable and delicate nature of quantum information makes it difficult to send tangled photons over long distances without interference. Longer optical fibers simply mean more opportunity for noise to interfere with tangled states.
In total, the lengths of fiber used to channel each cubit amounted to 44 kilometers, setting a new limit on how far we can send tangled qubits and still successfully use them to teleport quantum information.
Never before has it been demonstrated that it works over such a long distance with such precision and brings a quantum network the size of a city closer to reality – although there are still years of work ahead to make this possible.
“With this demonstration, we are starting to lay the groundwork for building a metropolitan quantum network in the Chicago area,” said Spentzouris.
Quantum entanglement and data teleportation are complex science, and even experts do not fully understand how they can be used in a quantum network. Each proof of concept like the one we get brings us a little closer to making this network happen.
In addition to promising huge increases in speed and computational power, a quantum internet would be ultra-secure – any hacking attempt would be as good as destroying the lock by being broken into. For now, at least, scientists think that quantum Internet networks will act as specialized extensions of the classical Internet, rather than a complete replacement.
Researchers are dealing with quantum internet problems from all different angles, which is why you will see a variety of distances mentioned in studies – they are not measuring the same technology, using the same equipment, to test the same patterns.
What makes this study special is the precision and distance of quantum entanglement teleportation, as well as the ‘off-the-shelf’ equipment used – theoretically it should be relatively easy to scale this technology using the hardware we already have.
“We are very proud to have reached this milestone in sustainable, high-performance and scalable quantum teleportation systems,” says physicist Maria Spiropulu of Caltech.
“The results will be further improved with the system updates that we hope to complete in the second quarter of 2021.”
The research was published in PRX Quantum.