From Santa Barbara, California to Hefei, China, scientists are developing a new kind of computer that will make today’s machines look like toys.
Harnessing the mysterious powers of quantum mechanics, the technology will perform tasks in minutes that even supercomputers could not perform for thousands of years. In fall 2019, Google unveiled an experimental quantum computer showing it was possible. Two years later, a lab in China did much the same thing.
But quantum computing won’t reach its potential without the help of another technological breakthrough. Call it a “quantum internet” – a computer network that can send quantum information between distant machines.
At Delft University of Technology in the Netherlands, a team of physicists has taken an important step towards this computer network of the future, using a technique called quantum teleportation to send data through three physical locations. Previously, this was possible with just two.
The new experiment indicates that scientists can extend a quantum network over an ever-increasing number of sites. “We are currently building small quantum networks in the lab,” said Ronald Hanson, the Delft physicist supervising the team. “But the idea is to eventually build a quantum internet.”
Their research, unveiled this week with an article published in the scientific journal Nature, demonstrates the power of a phenomenon that Albert Einstein once deemed impossible. Quantum teleportation – what he called “a frightening action at a distance” – can transfer information between locations without actually moving the physical matter that contains it.
This technology could profoundly change the way data travels from place to place. It’s based on over a century of research involving quantum mechanics, an area of physics that governs the subatomic realm and behaves unlike anything we experience in our daily lives. Quantum teleportation not only moves data between quantum computers, but it also does so in such a way that no one can intercept it.
“This means not only that the quantum computer can solve your problem, but also that it doesn’t know what the problem is,” said Tracy Eleanor Northup, a researcher at the Institute for Experimental Physics at the University of Innsbruck. , which also explores quantum teleportation. “It doesn’t work like that today. Google knows what you are running on its servers. »
A quantum computer taps into the strange ways certain objects behave if they are very small (like an electron or a particle of light) or very cold (like an exotic metal cooled to near absolute zero, or minus 460 degrees Fahrenheit). In these situations, a single object can behave like two separate objects at the same time.
Traditional computers perform calculations by processing “bits” of information, each bit containing either a 1 or a 0. By exploiting the strange behavior of quantum mechanics, a quantum bit, or qubit, can store a combination of 1s and 0 – much like how a spinning coin contains the tantalizing possibility that it will face or face when it finally falls flat on the table.
This means that two qubits can hold four values at once, three qubits can hold eight, four can hold 16, and so on. As the number of qubits increases, a quantum computer becomes exponentially more powerful.
Researchers believe these devices could one day speed up the creation of new drugs, advance artificial intelligence and summarily crack the encryption that protects computers vital to national security. Around the world, governments, university labs, start-ups and tech giants are spending billions of dollars exploring technology.
In 2019, Google announced that its machine had achieved what scientists call “quantum supremacy”, which meant it could perform an experimental task impossible with traditional computers. But most experts believe that it will still be several years – at the very least – before a quantum computer can actually do something useful that you can’t do with another machine.
Part of the challenge is that a qubit breaks, or “decoheres”, if you read information from it – it becomes an ordinary bit capable of holding only a 0 or a 1, but not the of them. But by chaining many qubits together and developing ways to guard against decoherence, scientists hope to build machines that are both powerful and practical.
Ultimately, ideally, these would be connected to networks capable of sending information between nodes, allowing them to be used from anywhere, much like the cloud services of Google and Google. ‘Amazon are making processing power widely available today.
But that comes with its own problems. Partly because of decoherence, quantum information cannot simply be copied and sent over a traditional network. Quantum teleportation offers an alternative.
Although it cannot move objects from place to place, it can move information by taking advantage of a quantum property called “entanglement”: a change in state of a quantum system instantly affects the status of another remote system.
“After entanglement, you can no longer describe these states individually,” Dr. Northup said. “Basically it’s now a system.”
These entangled systems could be electrons, light particles or other objects. In the Netherlands, Dr. Hanson and his team used what is called a nitrogen vacancy center – a tiny empty space in a synthetic diamond in which electrons can be trapped.
The team built three of these quantum systems, named Alice, Bob and Charlie, and connected them online with strands of fiber optics. Scientists could then entangle these systems by sending individual photons – particles of light – between them.
First, the researchers entangled two electrons, one belonging to Alice, the other to Bob. Indeed, the electrons received the same spin, and were therefore joined, or entangled, in a common quantum state, each storing the same information: a particular combination of 1 and 0.
The researchers could then transfer that quantum state to another qubit, a carbon nucleus, inside Bob’s synthetic diamond. This freed Bob’s electron, and the researchers were then able to entangle it with another electron belonging to Charlie.
By performing a specific quantum operation on Bob’s two qubits – the electron and the carbon nucleus – the researchers were then able to glue the two tangles together: Alice plus Bob glued to Bob plus Charlie.
The result: Alice got mixed up with Charlie, which allowed the data to teleport to all three nodes.
When data travels this way, without actually traveling the distance between nodes, it cannot be lost. “Information can be introduced on one side of the connection and then appear on the other,” Dr. Hanson said.
The information cannot be intercepted either. A future quantum internet, powered by quantum teleportation, could provide a new kind of theoretically unbreakable encryption.
In the new experiment, the network nodes weren’t that far apart – only about 60 feet. But previous experiments have shown that quantum systems can be entangled over longer distances.
The hope is that after several years of research, quantum teleportation will be viable for many miles. “We are now trying to do this outside of the lab,” Dr. Hanson said.