It’s not hyperbole to say that a quantum-powered internet would be revolutionary. It would allow quantum devices to deliver astonishing levels of privacy and security, and the computational clout to solve the kinds of complex problems that would fry a classical computer.
The countries and companies that have been busily laying the groundwork for a quantum internet have so far only been able to connect two quantum devices. But now, physicists at the Delft University of Technology in the Netherlands have successfully connected three quantum devices.
This may not sound like much, but in quantum computing terms it’s huge.
“This is the first time a network has been constructed from quantum processors,” lead study author Ronald Hanson tells Inverse. Hanson is an experimental physicist, Distinguished Professor at Delft University of Technology, and principal investigator at QuTech, a research center devoted to quantum computing and quantum internet.
“A single direct link between two processors has been shown on many platforms in the past decade, but no network had been achieved.”
These findings were published on Thursday in the journal Science.
What is the quantum internet?
Quantum computing enables powerful processing at more than a hundred million times the speed of a classical computer. Put simply, a quantum computer is capable of processing every possible answer to a problem simultaneously. How it does this is brain-meltingly complex because it harnesses the bizarre, and largely still pretty mysterious, behaviors of quantum physics.
Imagine the processing power of multiple quantum devices, or nodes, connected through a quantum internet. Experts predict that a global network of quantum computers could theoretically supply answers to some of our most challenging questions, like turning back climate change, curing disease, and solving world hunger. But the most immediate benefit is security.
“Quantum communication networks bring in a fundamentally new security paradigm, not threatened by any amount of computing power: the security is in the physics of it,” Harun Šiljak, an assistant professor at the School of Engineering at Trinity College Dublin, tells Inverse. Šiljak was not involved in the new study.
“When done right, such a secure communication protocol gives you the benefit of not having to trust anyone: hardware provider, software provider, network operator, or the state.”
Fully-realized quantum internet is still a far-off goal, but this three-node network brings it significantly closer.
Why this matters — The network developed by Hanson and colleagues brings us one step closer to the quantum internet – but we’re not there yet. Instead, it demonstrates how quantum devices could, with continued advances, communicate with each other over greater distances to create a functioning quantum internet in the near future.
“With this first network now achieved, we can start to use it as a unique testbed for quantum internet development,” Hanson says. “We will work on enhancing its functionality by increasing performance and increasing the number of qubits in the processors.”
Classical computers run on bits with values of 0 or 1. Quantum computers run on quantum bits – qubits – which can be both 0 and 1 at the same time in a state of ‘superposition’. The more qubits, the more quantum computers can do.
“The revolution in fields that eagerly wait for quantum computers is delayed while we try to figure out ways to make quantum computers at a larger scale: add more qubits,” Šiljak says.
But there’s a problem. Šiljak explains that the fragility of quantum processes means each new qubit brings a probability of an error. “Once errors happen, the computation is jeopardized,” Šiljak says. “Everything is connected, so an error in one part easily propagates and invalidates the entire computation.”
What’s next — Classical computers have error correction techniques, many of which rely on keeping and comparing multiple copies of data. But we can’t keep copies in the quantum realm. This is great for security, but bad when things go wrong. So how do we address errors?
“But to see the benefit for developing quantum systems over the next 10 years, we have to start now.”
It could come down to new ways of making quantum computers. A review published Thursday in the journal Science looks at the materials currently being used for key components in quantum devices – including superconducting qubits, semiconductor gate-defined quantum dots, and ions – and points toward new ways of developing materials that could improve and scale quantum hardware, as well as tackle the underlying causes of errors.
“For the materials community, developing new materials for QIP [Quantum Information Processing] platforms is a high priority,” explains co-author Hanhee Paik, an experimental quantum computing scientist at IBM Quantum.
“This includes replacing existing materials with better and more quantum-compatible materials and developing the fabrication methods to implement the new materials in the quantum hardware platform.”
Materials research also played an important role in advancing classical computing from transistors to integrated circuits, Paik says. For quantum computing to scale – to add more qubits, increase processing power and, ultimately, deliver the quantum internet – continued advancement in materials is crucial.
“This kind of effort takes time,” Paik says. “But to see the benefit for developing quantum systems over the next 10 years, we have to start now.”
Importantly, solving these material problems will take collaboration across disciplines, Paik and her team argue.
“Quantum computing began as a fundamentally interdisciplinary effort linking computer science, information science, and quantum physics,” the researchers write in the review. “The time is now ripe for expanding the field by including new collaborations and partnerships with materials science.”
This new study and the research from Delft University of Technology clearly demonstrate the need for joined-up approaches to resolving the obstacles in the way of getting quantum devices talking to each other, and finally realizing the dream of a quantum internet.
And, just like a particle in the quantum world, this dream now feels both possible and not possible at the same time.