June 3, 2021

A beam of ethereal blue laser light enters a specialized crystal. There it turns red, a sign that each photon has split into a pair with lower energies—and a mysterious connection. The particles are now quantum mechanically “entangled,” linked like identical twins who know each other’s thoughts despite living in distant cities. The photons zip through a tangle of fibers, then ever so gently deposit the information they encode into waiting clouds of atoms.

The transmogrifications are “a little bit like magic,” exults Eden Figueroa, a physicist at Stony Brook University. He and colleagues have concocted the setup on a few laboratory benches cluttered with lenses and mirrors. But they have a much bigger canvas in mind.

By year’s end, drivers in the largest U.S. metro areas—including, largely thanks to Figueroa, the suburbs of New York City—may unwittingly rumble over the tenuous strands of a new and potentially revolutionary network: a “quantum internet” stitched together by entangled photons like those in Figueroa’s lab.

Billions of dollars have poured into research on quantum computers and sensors, but many experts say the devices will flourish only when they are yoked to each other over long distances. The vision parallels the way the web vaulted the personal computer from a glorified typewriter and game console to an indispensable telecommunications portal. Through entanglement, a strange quantum mechanical property once derided by Albert Einstein as a “spooky distant effect,” researchers aim to create intimate, instantaneous links across long distances. A quantum internet could weld telescopes into arrays with ultrahigh resolution, precisely synchronize clocks, yield hypersecure communication networks for finance and elections, and make it possible to do quantum computing from anywhere. It could also lead to applications nobody’s yet dreamed of.

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