Quantum information is so fragile that a stray flicker of light can wreck it. So a team of physicists pushed it through a cable roaring with real internet traffic, just to see what would happen. Picture a strand of glass thinner than a human hair, buried beneath the streets between Evanston and downtown Chicago. Through it roars a flood of ordinary internet traffic: video calls, streaming movies, cloud backups. Each pulse of light contains millions of photons. Now imagine slipping a single, lonely photon instead – one carrying quantum information so delicate that a whisper of stray light can destroy it. Would anything survive the trip? Researchers at Northwestern University set out to answer exactly that. And the result could shape how the quantum internet – long promised, rarely seen outside a lab – actually gets built. Today’s internet stores information as bits, 0s and 1s. A future quantum internet would trade in quantum states instead, including entanglement – a strange link between two particles that holds true no matter how far apart they travel. Entangled photons could one day enable ultra-secure communication, connect quantum computers across cities, and even transfer quantum information without physically carrying it, through a process called teleportation. But there’s a catch, and it’s a big one. Quantum signals ride on single particles of light. Regular internet traffic blasts through fiber with overwhelming force. Study senior author Prem Kumar is a professor of electrical and computer engineering at Northwestern’s McCormick School of Engineering. Kumar directs the Center for Photonic Communication and Computing. Gina Talcott, a graduate student in his group, is the study’s first author. “Quantum signals are very, very tiny compared to classical signals,” said Kumar. “It’s like an ant traveling through a path filled with elephants. Our results show that photons can survive the