From Santa Barbara, California, to Hefei, China, scientists are developing a new type of computer that will make today’s machines look like toys.
Utilizing the mysterious powers of quantum mechanics, technology will perform tasks in minutes that even supercomputers could not complete for thousands of years. In the fall of 2019, Google unveiled an experimental quantum computer that shows this was possible. Two years later, a laboratory in China did almost the same thing.
But quantum computing would not be possible without the help of another technological breakthrough. Call it the “quantum internet” – a network of computers that can send quantum information between remote machines.
At Delft University of Technology in the Netherlands, a team of physicists has taken a major step towards this computer network of the future, using a technique called quantum teleportation to send data to three physical locations. Previously, this was only possible with two.
The new experiment shows that scientists can extend a quantum network to an increasing number of locations. “We are now building small quantum networks in the lab,” said Ronald Hanson, Delft’s physicist who oversees the team. “But the idea is to finally build a quantum Internet.”
Their research, unveiled this week in a paper published in the journal Nature, demonstrates the power of a phenomenon that Albert Einstein once considered impossible. Quantum teleportation – what he called “eerie action at a distance” – can transfer information between locations without actually moving the physical matter that holds them.
This technology could profoundly change the way data travels from place to place. It is based on more than a century of research involving quantum mechanics, a field of physics that governs the subatomic realm and behaves differently from anything we experience in our daily lives. Quantum teleportation not only moves data between quantum computers, but also does it in such a way that no one can intercept it.
“This not only means that the quantum computer can solve your problem, but also that it does not know what the problem is,” said Tracy Eleanor Northup, a researcher at the Institute for Experimental Physics at the University of Innsbruck who also studies quantum teleportation. “It does not work that way today. Google knows what you’re running on its servers. “
A quantum computer uses the strange way in which certain objects behave if they are very small (such as an electron or a particle of light) or very cold (such as an exotic metal that has cooled to almost zero or minus 460 degrees Fahrenheit). In these cases, a single object can behave like two separate objects at the same time.
Traditional computers perform calculations by processing “bits” of information, with each bit having either 1 or 0. Utilizing the strange behavior of quantum mechanics, a quantum bit or qubit can store a combination of 1 and 0 – a bit like how a rotating coin has the tempting chance of raising either its heads or its tails when it finally falls on the table.
This means that two qubits can hold four values at a time, 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 that these devices could one day accelerate the development of new drugs, accelerate advances in artificial intelligence and, in short, break the encryption that protects computers vital to national security. Governments, academia, start-ups, and tech giants around the world are spending billions of dollars exploring technology.
In 2019, Google announced that its engine had reached what scientists call “quantum superiority,” meaning it could perform experimental work that was impossible with traditional computers. But most experts believe it will be many more years — at least — before a quantum computer can actually do something useful that you can not do with another machine.
Part of the challenge is that a qubit breaks or “detunes” if you read information from it – it becomes an ordinary bit capable of holding only a 0 or a 1 but not both. But by combining many qubits together and developing ways to protect against incontinence, scientists hope to build machines that are both powerful and practical.
Eventually, they would ideally be integrated into networks that can send information between nodes, allowing them to be used from anywhere, such as cloud computing services such as Google and Amazon making processing power widely accessible today.
But this comes with its own problems. Partly because of withdrawal, quantum information cannot simply be copied and sent to a traditional network. Quantum teleportation provides 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 the state of one quantum system momentarily affects the state of another, remote system.
“After the entanglement, you can no longer describe these situations individually,” said Dr. Northup. “Basically, it’s a system now.”
These tangled systems could be electrons, light particles or other objects. In the Netherlands, Dr. Hanson and his team used what is called a nitrogen vacuum center – a tiny vacuum 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 to a line of fiber optic strands. Scientists could then integrate these systems by sending individual photons – light particles – between them.
First, the researchers trapped two electrons – one belonging to Alice and the other to Bob. In fact, the electrons were given the same spin, and thus joined, or entangled, in a common quantum state, each storing the same information: a specific combination of 1 and 0.
The researchers could then transfer this quantum state to another qubit, a carbon nucleus, inside Bob’s synthetic diamond. In this way the Bob’s electron was released and the researchers could then confuse it with another electron belonging to Charlie.
By performing a specific quantum operation on both of Bob’s qubits – the electron and the carbon nucleus – the researchers could then stick the two entanglements together: Alice plus Bob stuck to Bob plus Charlie.
The result: Alice became entangled with Charlie, which allowed data to be teleported to all three nodes.
When data travels this way, without actually traveling the distance between nodes, it cannot be lost. “Information can be fed to one side of the link and then displayed on the other,” said Dr. Hanson.
The information also can not be intercepted. A future quantum Internet powered by quantum teleportation could offer a new kind of encryption that is theoretically unbreakable.
In the new experiment, the network nodes were not that far apart – only about 60 feet. But previous experiments have shown that quantum systems can be involved over longer distances.
The hope is that, after several years of research, quantum teleportation will be viable in many miles. “Now we’re trying to do that outside of the lab,” Dr. Hanson said.