It takes little more than logging on to see the flaws in today's internet — mainly, how easy it is to steal or intercept data. One future solution for these problems could be an upgrade that relies on the latest advances in the science of subatomic particles: a quantum internet.
Just last week, three scientists from the renowned QuTech centre at the
Delft University of Technology (TU Delft) revealed a roadmap for how this quantum internet should develop. They also plan to connect four cities with a quantum link by 2020, reports MIT Tech Review. And today, University of Chicago scientists announced that they plan to set up a quantum link across a 48km distance. Scientists are really getting serious about this quantum internet idea.
"I think it's useful to have a vision if you want to put something into the real world," Stephanie Wehner, a professor in quantum information at TU Delft and roadmap co-author, told Gizmodo. "We hoped to offer guidelines for people who want to implement these networks in the real world."
A quantum internet isn't an upgrade to the regular internet so much as an addendum. According to the roadmap, which is published in Science, "the vision of a quantum internet is to provide fundamentally new internet technology by enabling quantum communication between any two points on Earth." As is generally the case with nascent technology, it's not clear what all of the uses for a quantum internet would be just yet.
But there are already a few ideas. Perhaps it will offer increased cybersecurity, help to better synchronise clocks, improve telescope networks like the ones hoping to image the Milky Way's central black hole, enhance sensor technology, or allow access to the power of a quantum computer processor via the cloud.
Such a network differs from a classical network at its very core. The internet transmits data translated into fundamental units called bits, always equal to either zero or one. A quantum internet could transmit qubits, which take on a superposition of zero and one, meaning they can have values that are partially zero and partially one at the same time. Some hope that qubits can allow for more powerful computations with richer sub-components.
They also offer some communications advantages. You can entangle qubits, meaning that they're treated mathematically as single units regardless of the separation between them. Qubits cannot be copied — any attempt to do so would be detected. Qubits automatically turn into zero or one as soon as they're measured (based on a probability encoded into the qubit's value).
Quantum communication might allow you to perform calculations on the quantum cloud without the quantum computer knowing what computation it has done. Or you could entangle a qubit over a long distance — if measured, the two entangled qubits could take on the same random answer when measured, impossible to be predetermined and impossible for a third party to know.
Wehner and her collaborators' paper sets forth a roadmap to achieve the quantum internet dream. Such a project would require a quantum channel, or a physical link to transmit qubits; it would need quantum repeaters that would allow for two qubits to entangle over large distances; and finally, it would require quantum end nodes that could be a simple as devices that measure the qubits' values or full-scale quantum computer processors.
Step one would be a repeater network, where points connected to the repeater can receive quantum encryption keys (but quantum information can't be transmitted). Step two would be a network where any node can send a qubit to any other. Step three allows entanglement between any two nodes. Step four allows the nodes to actually store the quantum state. The final two stages involve actually hooking up and linking quantum processors to allow for computations over the link.
The paper is an important work; a "manifesto for the quantum internet," Ciaran Lee, research fellow at the University College London, told Gizmodo. "The great thing about the way these stages have been set out is that asour technological capabilities improve, and we move up from a stage, completely new applications become available that weren't possible at the previous stage." Each step offers a benefit the previous one lacked.
There are challenges along the way, of course. We're at phase one, though some experiments are already working at more advanced pieces of the network. But all of the challenges of quantum computing, such as how easily qubits fall apart into regular bits, apply here. Wehner thought the biggest present-day limitation is that, said simply, it takes too long to generate entanglement.
Experiments are underway to advance the state of these quantum networks, including the quantum network in the Netherlands planned for 2020. China also has a satellite, Micius, used for quantum experiments, though qubit valuescan't be stored or manipulated at the nodes (it's always measured as either zero or one, instead of returning a manipulatable quantum state).
Though Wehner noted that the United States has previously been a little quiet in terms of support for quantum internet research, things are intensifying. The newly announced project, funded by the US Department of Energy and led by University of Chicago researchers, it currently testing entanglement across 48km over a previously dormant fibre-optic link.
Again, it's early days, and the field is still relatively small. "We need to train a generation of students who will be the future users of this technology," David Awschalom, University of Chicago quantum information professor, told Gizmodo. "One nice thing about building a quantum platform like ours is that it will provide an enormous educational platform."
Will the quantum internet ever truly be realised? Who knows — but at least there's a plan.