In the cool October air of 2024, two snapshots—a portion of the Great Wall of China and a sun-drenched courtyard at South Africa’s Stellenbosch University—traveled across space, encrypted in pulses of quantum light. The photos were unremarkable. The way they traveled was anything but.
From a rooftop in Beijing to a telescope in South Africa, 12,900 kilometers away, scientists pulled off a feat no one had ever accomplished: sending quantum-encrypted data over nearly one-third of Earth’s circumference using a small, cost-efficient satellite no larger than a suitcase. A new study now documents the results of this breakthrough experiment.
For years, scientists have touted quantum key distribution (QKD) — a method of encrypting messages using the fundamental laws of physics — as the future of secure communication. But implementing it over long distances has proven difficult. Fiber-optic cables lose photons. Large satellites are expensive and unwieldy. And the ground stations needed to catch these delicate quantum signals are often the size of shipping containers.
“It’s a significant milestone,” said Jian-Wei Pan, the physicist who led the project from the University of Science and Technology of China.
We’re now a step closer to a global internet secured by the laws of physics.
A Quantum Postman in Orbit
The satellite, dubbed Jinan-1, orbits Earth at about 500 kilometers altitude in a Sun-synchronous orbit. While previous missions like Micius — the world’s first quantum satellite launched in 2016 — proved QKD was possible, they relied on satellites weighing over 600 kilograms and ground stations that tipped the scales at 13,000 kilograms. In contrast, the Jinan-1 payload weighs just 23 kilograms. Its companion ground stations are a trim 100 kilograms.
This dramatic miniaturization didn’t come at the cost of performance. In fact, Jinan-1 delivers real-time key generation with multiple portable ground stations across China and even South Africa — over 12,900 kilometers away.
“We achieve the sharing of up to 1.07 million bits of secure keys during a single satellite pass,” the study reports.
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And that wasn’t a one-off success. Over 20 satellite passes spanning urban rooftops and mountain outposts, the researchers repeatedly generated hundreds of thousands of secure bits, all in real time.
“We want to improve the technology from proof-of-principle to really practical and useful,” Pan told Nature. That practicality could arrive as early as 2027, when China plans to offer commercial quantum communication services to millions, in partnership with China Telecom.
The European Union, meanwhile, is racing to build its own secure satellite network through the SAGA initiative, and companies like Thales Alenia Space and Boeing are preparing launches of their own.
Why Quantum Matters
The crux of QKD is that measuring a quantum bit (or qubit) disturbs it.
The Jinan-1 satellite used pulses of laser light, each in a quantum state of “superposition” — representing both 1 and 0 simultaneously. When the sender and receiver compare measurements, they can extract a shared string of bits to use as a key. And if anyone tries to intercept it, the fragile quantum states collapse, revealing the eavesdropper.
Using photons encoded with the BB84 protocol — a standard in quantum cryptography — the microsatellite sends quantum keys to ground stations. The team integrated a custom-built 625-MHz QKD light source powered by a single laser diode, paired with a compact telescope and a smart tracking system that allows the satellite to follow ground stations with microradian accuracy. Any errors in the key hint at interference, allowing users to discard compromised bits.
Today’s encryption schemes could one day be rendered obsolete by powerful quantum computers. But QKD is designed to resist that future threat.
“This provides very strong assurance that a future quantum computer cannot read confidential communications,” said Alexander Ling, a physicist at the National University of Singapore and co-founder of the QKD firm SpeQtral.
While banks and governments already use QKD over fiber optics, the reach is limited. Satellite-based systems — especially ones this light and affordable — could scale globally.
But the current system isn’t flawless. Jinan-1 doesn’t use entangled photons, which would allow even more secure communication where not even the satellite knows the key. If the satellite were hacked, the key could be compromised. “Miniaturizing the technology for entanglement is harder,” Pan admitted, but said it is “entirely feasible” in the future.
What’s Next?
This research offers a template for a future in which fleets of small satellites crisscross the sky, beaming down quantum keys to users as casually as GPS signals. The team is already planning to scale up, launching multiple microsatellites and deploying more portable ground stations.
They’re also eyeing upgrades like photonic chip-based QKD sources, daytime quantum communication, and integration with existing internet satellites. These would enable 24/7 coverage and global reach.
If successful, it won’t just be governments encrypting sensitive messages. Anyone — from banks to hospitals to journalists — could one day plug into a quantum-secured channel as easily as opening a secure webpage.
The findings appeared in the journal Nature.
