From Santa Barbara, California, to Hefei, China, scientists are developing a new type of computer that makes today’s machines more like games.
By harnessing the mysterious powers of quantum mechanics, the technology will perform tasks in minutes that even supercomputers have not been able to complete for thousands of years. In the fall of 2019, Google unveiled an experimental quantum computer showing that this is possible. Two years later, a laboratory in China did the same.
But quantum computing wouldn’t reach its potential without the help of another technological breakthrough. He called it the “quantum internet” – a computer network that can send quantum information between remote devices.
At Delft University of Technology in the Netherlands, a team of physicists has taken an important step toward this future computer network, using a technique called quantum teleportation to send data across three physical locations. Previously, this was possible with only two.
The new experiment indicates that scientists can extend a quantum network across an increasing number of sites. “We are now building small quantum networks in the lab,” said Ronald Hanson, a Delft physicist who leads the team. “But the idea is to eventually build a quantum internet.”
Their research, revealed this week in a paper published in the scientific journal Nature, shows the power of a phenomenon that Albert Einstein once considered impossible. Quantum teleportation – what he called a “remote scare action” – can transmit information between locations without moving the physical matter that holds it.
This technology could profoundly change the way data travels from one place to another. It is based on more than a century of research involving quantum mechanics, a field of physics that governs the subatomic world and behaves unlike anything we experience in our daily lives. Quantum teleportation not only transmits data between quantum computers, but it also does so in a way that no one can intercept.
“Not only does this mean that a quantum computer can solve your problem, but it also doesn’t know what the problem is,” said Tracy Eleanor Northup, a researcher at the Institute of Experimental Physics at the University of Innsbruck who is also exploring quantum teleportation. “It doesn’t work that way today. Google knows what you’re running on its servers.”
A quantum computer deals with the strange ways that some things behave if they are very small (such as an electron or a particle of light) or extremely cold (such as a strange metal being cooled to nearly absolute zero, or minus 460 degrees Fahrenheit). In these cases, a single object can act as two separate objects at the same time.
Traditional computers perform calculations by processing “bits” of information, with each bit containing either a 1 or a 0. Harnessing the strange behavior of quantum mechanics, a quantum bit, or qubit, can store a combination of 1 and 0 – a bit like the way The spinning coin has the tantalizing possibility that it will either appear as a head or a tail when it finally falls 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 quantum qubits grows, a quantum computer becomes more and more powerful.
Researchers believe these devices could one day speed up the creation of new drugs, power advances in artificial intelligence, and crack the encryption that protects computers vital to national security. All over the world, governments, academic labs, startups, and tech giants are spending billions of dollars exploring technology.
In 2019, Google announced that its devices had reached what scientists call “quantum supremacy,” meaning they could perform an experimental task that was impossible with conventional computers. But most experts believe it will be at least several more years 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 “disassembles”, if you read information from it – it becomes a regular bit capable of holding only 0 or 1 but not both. But by linking many qubits together and developing ways to guard against decoherence, scientists hope to build powerful and practical machines.
Ultimately, ideally, these networks will be joined to networks that can send information between nodes, allowing it to be used from anywhere, just as cloud computing services from the likes of Google and Amazon allow processing power to be accessed at scale today.
But this comes with its own problems. Partly because of decoherence, quantum information cannot be copied and transmitted over a traditional network. Quantum teleportation provides an alternative.
Although it cannot move objects from one place to another, it can transmit information by taking advantage of a quantum property called “entanglement”: any change in the state of a quantum system that immediately affects the state of another system that is far away.
“After the crossover, you can no longer describe these conditions individually,” said Dr. Northup. “Essentially, it is now one system.”
These entangled systems can be electrons, light particles, or other things. In the Netherlands, Dr. Hanson and his team used what’s called a vacant nitrogen center – a small empty space in synthetic diamond where electrons can be trapped.
The team built three of these quantum systems, named Alice, Bob and Charlie, and connected them in line with fiber-optic strands. Scientists can then entangle these systems by sending individual photons – particles of light – between them.
First, the researchers entangled two electrons – one belonging to Alice and the other to Bob. In fact, the electrons were given the same spin, and thus were joined or entangled, in a common quantum state, each storing the same information: a certain combination of 1 and 0.
The researchers can then transfer this quantum state to another qubit, the carbon nucleus, within Bob’s synthetic diamond. Doing so freed Bob’s electron, and the researchers could then link it to another electron belonging to Charlie.
By performing a specific quantum operation on each of Bob’s qubits – the electron and the carbon nucleus – the researchers can then glue the two entanglements together: Alice and Bob are glued to Bob and Charlie.
The result: Alice was entangled with Charlie, allowing the data to teleport instantly through all three nodes.
When data travels in this way, without actually moving the space between nodes, it cannot be lost. “Information can be entered on one side of the connection and then shown on the other,” Dr. Hanson said.
The information also cannot be intercepted. The quantum internet of the future, powered by quantum teleportation, could provide a new type of theoretically unbreakable cryptography.
In the new experiment, the network’s nodes weren’t far apart — only about 60 feet. But previous experiments have shown that quantum systems can get entangled over longer distances.
The hope is that after several more years of research, quantum teleportation will be viable across many miles. “We’re now trying to do it outside of the lab,” Dr. Hanson said.