November 28, 2022

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, the technology will do in minutes what even supercomputers have been unable to do for thousands of years. In the fall of 2019, Google unveiled an experimental quantum computer that showed it was possible.Two years later, a laboratory in China did a lot of the same.

But quantum computing won’t reach its potential 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 toward the computer network of the future, using a technique called quantum teleportation to send data across three physical locations. Previously, only two could do this.

New experiments show that scientists can scale quantum networks across a growing number of sites. “We are now building small quantum networks in the laboratory,” said Delft physicist Ronald Hanson, who led the team. “But our idea is to eventually build a quantum internet.”

Their study was published this week A paper published in the scientific journal Nature, demonstrating the power of phenomena that Albert Einstein once thought impossible. Quantum teleportation – he called it “horror from afar“—information can be transferred between locations without actually moving the physical matter that holds it.

This technology could profoundly change the way data is transferred from one place to another. It draws on more than a century of research involving quantum mechanics, a field of physics that dominates the subatomic realm and behaves differently than anything we experience in our daily lives. Quantum teleportation not only moves data between quantum computers, but also in a way that no one can intercept.

“Not only does this mean that a quantum computer can solve your problem, but it doesn’t know what the problem is,” says 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.”

If certain objects are very small (like electrons or particles of light) or very cold (like exotic metals cooled to almost absolute zero or minus 460 degrees Fahrenheit), quantum computers take advantage of the strange way they behave. In these cases, a single object can behave like two separate objects at the same time.

Traditional computers perform computations by manipulating “bits” of information, each bit containing either a 1 or a 0. By exploiting the strange behavior of quantum mechanics, a qubit or qubit can store a combination of 1s and 0s – a little like how a spinning coin holds the tantalizing possibility that when it ends up flat on a table it will Appears head or tail.

This means that two qubits can hold four values ​​at the same time, three qubits can hold eight, four can hold 16, and so on. As the number of qubits grows, the capabilities of quantum computers will increase exponentially.

Researchers believe these devices could one day accelerate the development of new drugs, advance advances in artificial intelligence, and quickly crack the encryption that protects computers vital to national security. Globally, governments, academic labs, start-ups and tech giants are spending billions to explore the technology.

In 2019, Google announced that its machine had achieved what scientists call “quantum supremacy,” meaning it can perform experimental tasks that conventional computers can’t. But most experts believe it will be at least a few more years — at least — before quantum computers can actually do something useful that you can’t do with another machine.

Part of the challenge is that if you read from it, the qubit breaks or “falls out” — it becomes a normal bit that can only hold 0 or 1, but not both. But by stringing together many qubits and developing ways to prevent decoherence, scientists hope to make machines that are both powerful and practical.

Ultimately, ideally, these will be joined to networks that can send information between nodes, allowing them to be used anywhere, just as cloud computing services from companies like Google and Amazon make processing power widely available today.

But this also has its own problems. Due in part to decoherence, quantum information cannot simply be copied and sent over traditional networks. Quantum teleportation offers another option.

While it can’t move objects from one place to another, it can move information using a quantum property called “entanglement”: a change in the state of one quantum system instantly affects the state of another, distant quantum system.

“After entanglement, you can no longer describe these states individually,” Dr. Northup said. “Fundamentally, it’s a system now.”

These entangled systems could be electrons, particles of light, or other objects. In the Netherlands, Dr Hansen and his team used so-called nitrogen vacancy centers – tiny spaces in synthetic diamonds where electrons can be trapped.

The team constructed three quantum systems, named Alice, Bob, and Charlie, and connected them in a straight line with multiple strands of optical fiber. 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 effect, the electrons are given the same spin and thus bind or entangle together in a common quantum state, each storing the same information: a specific combination of 1s and 0s.

The researchers could then transfer this quantum state to another qubit within Bob’s synthetic diamond, the carbon nucleus. Doing so freed Bob’s electron, which the researchers could then entangle with another electron belonging to Charlie.

By performing specific quantum operations on Bob’s two qubits (the electron and the carbon core), the researchers were able to bond the two entanglements together: Alice plus Bob bond to Bob plus Charlie.

Result: Alice is entangled with Charlie, which allows data to travel across all three nodes.

When data is transmitted in this way, there is no need to actually transmit the distance between nodes, and there is no loss. “Information can be fed into one side of the connection and then appear on the other side,” Dr. Hansen said.

Information also cannot be intercepted. A future quantum internet powered by quantum teleportation could provide a theoretically unbreakable new type of encryption.

In the new experiment, the network nodes were not far apart—only about 60 feet apart. 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 able to span miles. “We’re now trying to do this outside the lab,” said Dr. Hansen.



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