From Santa Barbara, California, to Hefei, China, scientists are developing a new type of computer that will make today’s machines look like toys.
Harnessing the mysterious power of quantum mechanics, this technology will perform tasks in minutes that even supercomputers cannot complete in thousands of years. In the fall of 2019, Google unveiled an experimental quantum computer that demonstrated this was possible. Two years later, a laboratory in China did the same thing.
But quantum computing will not reach its potential without the help of other technological breakthroughs. Call it the “quantum internet” — a network of computers that can send quantum information between distant machines.
At Delft University of Technology in the Netherlands, a team of physicists has taken a significant step toward this future computer network, using a technique called quantum teleportation to send data across three physical locations. Previously, this was only possible with two.
New experiments show that scientists can stretch quantum networks across an ever-larger number of sites. “We’re now building a small quantum network in the lab,” said Ronald Hanson, the Delft physicist who oversaw the team. “But the idea is to eventually build a quantum internet.”
Their research, launched this week with a paper published in the science journal Nature, demonstrates the power of a phenomenon once thought impossible by Albert Einstein. Quantum teleportation – what he calls “spooky action at a distance” – can transfer information between locations without actually moving the physical material that holds it back.
This technology can greatly change the way data moves from one place to another. It draws on more than a century of research involving quantum mechanics, the field of physics that governs the subatomic realm and behaves unlike anything we experience in our daily lives. Quantum teleportation not only transfers data between quantum computers, it does so in such a way that nothing can intercept it.
“This not only means that a 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 University of Innsbruck’s Institute of Experimental Physics who is also exploring quantum teleportation. “It didn’t work like that today. Google knows what you’re running on its servers.”
Quantum computers take advantage of the strange way some objects behave if they are very small (such as electrons or light particles) or very cold (such as an exotic metal cooled to near absolute zero, or minus 460 degrees Fahrenheit). In this situation, one object can behave like two separate objects at the same time.
Traditional computers perform calculations by processing “bits” of information, with each bit holding a 1 or 0. By taking advantage of the odd behavior of quantum mechanics, quantum bits, or qubits, can store combinations of 1s and 0s — a bit like how a coin is Spinning has the tantalizing possibility that the coin will appear either heads or tails 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, quantum computers become exponentially more powerful.
Researchers believe these devices could one day accelerate the creation of new drugs, advance the power of artificial intelligence and rapidly crack encryption that protects computers critical to national security. Around the world, governments, academic labs, startups, 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 means it can perform experimental tasks that would be impossible with traditional computers. But most experts believe it will be a few more years – at least – before quantum computers can actually do something useful that you can’t do with other machines.
Part of the challenge is that qubits break, or “decoheres”, if you read the information from them — they become regular bits capable of only 0 or 1 but not both. But by stringing multiple qubits together and developing ways to prevent decoherence, scientists hope to build a machine that’s both robust and practical.
Ultimately, ideally, these will be combined into a network that can transmit information between nodes, allowing them to be deployed from anywhere, just as cloud computing services like Google and Amazon make processing power widely accessible today.
But this comes with its own problems. Partly because of decoherence, quantum information cannot simply be copied and transmitted over traditional networks. Quantum teleportation provides an alternative.
While it cannot move objects from one place to another, it can move information by utilizing a quantum property called “entanglement”: A change in the state of one quantum system instantaneously affects the state of another distant quantum system.
“After the entanglement, you can no longer describe these states individually,” says Dr. Northup. “Basically, now it is one system.”
These entangled systems can be electrons, light particles or other objects. In the Netherlands, Dr. Hanson and his team used what’s called a nitrogen vacancy center — a tiny empty space in synthetic diamond where electrons can be trapped.
The team built these three quantum systems, named Alice, Bob and Charlie, and connected them in a line with optical fiber strands. Scientists can then ensnare this system by sending individual photons – particles of light – between them.
First, the researchers entangled two electrons — one belonging to Alice, the other to Bob. As a result, the electrons are given the same spin, and are thus joined, or entangled, in a generalized quantum state, each storing the same information: a certain combination of 1’s and 0’s.
The researchers were then able to transfer this quantum state to another qubit, the carbon core, inside Bob’s synthetic diamond. Doing so frees Bob’s electrons, and the researchers can then associate them with Charlie’s other electrons.
By performing specific quantum operations on Bob’s two qubits — the electron and the carbon nucleus — the researchers were then able to glue the two entanglements together: Alice plus Bob fixated on Bob plus Charlie.
The result: Alice becomes entangled with Charlie, which allows data to teleport across all three nodes.
When data travels this way, without actually traveling the distance between nodes, data cannot be lost. “Information can be entered on one side of the connection and then appear on the other side,” says Dr. Hanson.
The information also cannot be intercepted. The future quantum internet, powered by quantum teleportation, could provide a new, theoretically unbreakable type of encryption.
In the new experiment, the network nodes weren’t far apart — only about 60 feet. But previous experiments have shown that quantum systems can be entangled over greater distances.
The hope is that, after a few more years of research, quantum teleportation will be able to travel for miles. “We’re now trying to do this outside the lab,” said Dr. Hanson.
