A quantum Internet could be useful for a number of situations such as sending unhackable messages and improving GPS accuracy. Scientists around the world have been working on realizing a quantum network for over 20 years. The biggest roadblock has been sending quantum signals across long distances.
Now, a team of researchers from MIT and Harvard University in the U.S. has found the "missing link" for a practical quantum Internet.
Their findings were published in Nature on Monday.
Modern version of an old idea
The researchers' method is essentially a modern twist on an old-fashioned idea of a repeater, which enables communication at long distances by correcting and compensating for signal loss.
The researchers have created a prototype quantum node that can catch, store, and entangle bits of quantum information.
"This demonstration is a conceptual breakthrough that could extend the longest possible range of quantum networks and potentially enable many new applications in a manner that is impossible with any existing technologies," said Mikhail Lukin of Harvard.
Entanglement is the crucial part of the study, as it enables information to be perfectly correlated over long distances — this way no one can listen in. Currently, quantum communication experiences photon loss over long distances, which is one of the biggest challenges for scientists looking to improve large-scale quantum computing.
Lukin and his colleagues have been working hard on harnessing a system that can perform two tasks well: catching and processing quantum bits of quantum information, and storing them long enough for all of the networks to be ready.
The researchers have integrated an individual color center in a prefabricated diamond cavity, which forces the photons to be confined and to interact with the single color center.
Their device can store quantum information in milliseconds — enough time to transport information over thousands of kilometers.
"This device combines the three most important elements of a quantum repeater – a long memory, the ability to efficiently catch information off photons, and a way to process it locally," said Bart Machielse of Harvard.
"Each of those challenges have been addressed separately but no one device has combined all three."