Quantum Internet Is 13 Years Away. Wait, What’s Quantum Internet? – WIRED

A year ago this week, Chinese physicists launched the worlds first quantum satellite. Unlike the dishes that deliver your Howard Stern and cricket tournaments, this 1,400-pound behemoth doesnt beam radio waves. Instead, the physicists designed it to send and receive bits of information encoded in delicate photons of infrared light. Its a test of a budding technology known as quantum communications, which experts say could be far more secure than any existing info relay system.

Theyve kept the satellite busy. This summer, the group has published several papers in Science and Nature in which they sent so-called entangled photons between the satellitenicknamed Micius, after an ancient Chinese philosopherand multiple ground stations. If quantum communications were like mailing a letter, entangled photons are kind of like the envelope: They carry the message and keep it secure. Jian-Wei Pan of the University of Science and Technology of China, who leads the research on the satellite, has said that he wants to launch more quantum satellites in the next five years. By 2030, hes hoping that quantum communications will span multiple countries. In 13 years, you can expect quantum internet.

Which means what exactly? In the simplest terms, it will involve multiple parties pinging information at each other in the form of quantum signalsbut experts havent really figured out what it will do beyond that. Quantum internet is a vague term, says physicist Thomas Jennewein of the University of Waterloo. People, including myself, like to use it. However, theres no real definition of what it means.

Thats because so much of the technology is still in its infancy. Physicists still cant control and manipulate quantum signals very well. Pans quantum satellite may have been able to send and receive signals, but it cant really store quantum informationthe best quantum memories can only preserve information for less than an hour. And researchers still dont know what material makes the best quantum memory.

They also arent sure how theyd transmit signals efficiently between the nodes of the future quantum web. Blanketing Earth in quantum satellites is expensivePans cost $100 million. Ground-based transmission via optical fiber isnt perfect either: Quantum signals die out after about 60 miles of transmission. The signals cant be amplified like an electronic signal, either. So researchers are developing special devices known as quantum repeaters that can transmit signals over long distances.

That research will take time. Even if Pan gets his international network up and running by 2030, its not like itll be handling your social media feed by then. And maybe we wouldnt want it to, either. Just because something is quantum doesnt mean its automatically better, says physicist Kai-Mei Fu of the University of Washington. In many cases, it doesnt make a lot of sense to communicate quantum mechanically, she says. Quantum signals have weird properties like superposition, where a particles location is a probability distribution, and it has no precise location. Most communication between humans would still be far easier to express by encoding regular old 1s and 0s in blips of electricity.

So whats the point of it? In the near future, the quantum internet could be a specialized branch of the regular internet. Research groups all over the world are currently developing chips that might allow a classical computer to connect to a quantum network. People would use classical computing most of the time and hook up to the quantum network only for specific tasks.

For example, says physicist Renato Renner of ETH Zurich, you might connect a classical personal computer to a quantum network to send a message using quantum cryptographyarguably the most mature quantum technology. In quantum cryptography, a sender uses a cryptographic key encoded in a quantum signal to encrypt a message. According to the laws of quantum mechanics, if someone tried to intercept the key, they would destroy it.

The quantum internet could also be useful for potential quantum computing schemes, says Fu. Companies like Google and IBM are developing quantum computers to execute specific algorithms faster than any existing computer. Instead of selling people personal quantum computers, theyve proposed putting their quantum computer in the cloud, where users would log into the quantum computer via the internet. While running their computations, they might want to transmit quantum-encrypted information between their personal computer and the cloud-based quantum computer. Users might not want to send their information classically, where it could be eavesdropped, Fu says.

But itll take a whileif everbefore a quantum network gets as big or as versatile as our current internet. To get to the point where billions of quantum devices are connected to the same network, where any connected device can talk to any other device, wed be lucky to see it in our lifetime, Jennewein says.

The incremental progress doesnt bother Renner. Hes just excited that these experiments inspire physicists to think about quantum mechanics in new ways. All these developments will certainly help our understanding of physics, he says. As a physicist, I want to stress that we are not only application-driven, but also driven by our search for understanding. As consumers, though, well be waiting for our new gadgets.

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Quantum Internet Is 13 Years Away. Wait, What's Quantum Internet? - WIRED

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