A YEAR AGO this week, Chinese physicists launched the world’s first #quantumsatellite . Unlike the dishes that deliver your Howard Stern and cricket tournaments, this 1,400-pound behemoth doesn’t beam radio waves. Instead, the physicists designed it to send and receive bits of information encoded in delicate photons of infrared light. It’s a test of a budding technology known as quantum communications, which experts say could be far more secure than any existing info relay system. They’ve 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 satellite—nicknamed Micius, after an ancient Chinese philosopher—and 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, he’s 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 signals—but experts haven’t 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, there’s no real definition of what it means.” That’s because so much of the technology is still in its infancy. Physicists still can’t control and manipulate quantum signals very well. Pan’s quantum satellite may have been able to send and receive signals, but it can’t really store quantum information—the best quantum memories can only preserve information for less than an hour. And researchers still don’t know what material makes the best quantum memory. They also aren’t sure how they’d transmit signals efficiently between the nodes of the future quantum web. Blanketing Earth in quantum satellites is expensive—Pan’s cost $100 million. Ground-based transmission via optical fiber isn’t perfect either: Quantum signals die out after about 60 miles of transmission. The signals can’t 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, it’s not like it’ll be handling your social media feed by then. And maybe we wouldn’t want it to, either. Just because something is “quantum” doesn’t mean it’s automatically better, says physicist Kai-Mei Fu of the University of Washington. “In many cases, it doesn’t make a lot of sense to communicate quantum mechanically,” she says. Quantum signals have weird properties like superposition, where a particle’s 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 1’s and 0’s in blips of electricity. So what’s 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.
https://www.wired.com/story/quantum-internet-is-13-years-away-wait-whats-quantum-internet/
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