For 15 days last December, a complex quantum operation took place deep under New York City. Photons of light streamed around an area stretching from the Brooklyn Navy Yard to Corona, Queens, forming a 21-mile-long (34-kilometer-long) quantum network beneath the metropolis.
Quantum hardware company Qunnect ran the experiment on its GothamQ testbed. The quantum network operated on existing optical fibers that make up some of New York’s telecommunications infrastructure. The key difference between traditional subterranean telecoms and the recent experiment is that, instead of ordinary photons traveling through the cables, the Qunnect team transmitted entangled, polarized photons—that is, photons in a quantum state. The team’s research is published in PRX Quantum.
“It’s always hard to explain what a next-generation infrastructure is going to do for you. Often the people inventing the infrastructure don’t know,” said Mehdi Namazi, a quantum physicist and the Chief Science Officer at Qunnect, in a video call with Gizmodo. “It’s very hard to say what will be the use case, because that’s like defining what would’ve been the application of the internet.”