In the fresh air of October 2024, two snapshots, a portion of the Great Wall of China and a patio bathed by the Sun at the University of Stellenbosch in South Africa, enter through space, encrypted in pulses of quantum light. The photos were not notable. The way they traveled was the opposite.
From a roof in Beijing to a telescope in South Africa, 12,900 kilometers away, the scientists achieved a feat that no one had achieved: sending data complemented with when in almost a third of the land circumference using a small profitable satellite that is not larger than a suitcase. A new study now documents the results of this great experiment.
For years, scientists have promoted the distribution of quantum key (QKD), a method to encrypt messages using the fundamental laws of physics, such as the future of safe communication. But implementing it in long distances has been difficult. Fiber optic cables lose photons. Large satellites are expensive and difficult to handle. And the necessary terrestrial stations to catch these delicate quantum signals are often the size of the shipping containers.
“It’s a significant milestone,” said Jian-Wei Pan, the physicist who directed the Chinese University and Technology project.
Now we are one step closer to a global Internet assured by the laws of physics.
A quantum postman in orbit
The satellite, bent Jinan-1Orbit the Earth about 500 kilometers of altitude in a solar synchronous orbit. While previous missions like Micius – The first quantum satellite of the world launched in 2016, showed that QKD was possible, trusted satellites that weighed more than 600 kilograms and terrestrial stations that inclined the balance to 13,000 kilograms. In contrast, Jinan-1 payload weighs only 23 kilograms. Its complementary land stations are an adjustment of 100 kilograms.
This dramatic miniaturization did not reach the expense of performance. In fact, Jinan-1 offers a key generation in real time with multiple portable land stations in China and even South Africa, more than 12,900 kilometers away.
“We managed to share up to 1.07 million bits of safe keys during a single satellite pass,” the study reports.
And that was not a unique success. More than 20 satellite passes that cover urban fabrics and mountain advances, the researchers repeatedly generated hundreds of thousands of safe bits, all in real time.
“We want to improve proof technology to really practical and useful,” PAN told Nature. That practicality could come as soon as 2027, when China plans to offer commercial services of quantum communication to millions, in association with China Telecom.
Meanwhile, the European Union is running to build its own safe satellite network through the Saga initiative, and companies such as Thales Alenia Space and Boeing are preparing their own launch.
Why quantum matters
QKD quid is that the measurement of a quantum drill (or qubit) disturbs it.
The Jinan-1 satellite used laser light pulses, each in a quantum state of “overlap”, which represents 1 and 0 simultaneously. When the sender and receiver compare the measurements, they can extract a shared bits chain to use as a key. And if someone tries to intercept it, fragile quantum states collapse, revealing Spanish.
Use of photons encoded with the BB84 protocol, a standard in quantum cryptography, microsatellites send quantum key to terrestrial stations. The team integrated a 625 MHz Customized Light Source fueled by a single laser diode, matched with a compact telescope and an intelligent follow -up system that allows the satellite to follow the earth stations with microradian precision. Any mistake in the key suggests interference, which allows users to discard compromised bits.
Today’s encryption schemes one could someday become obsolete for the powerful quantum computers. But QKD is designed to resist that future threat.
“This provides a very solid guarantee 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 Speqtral QKD firm.
While banks and governments already use QKD on fiber optics, the scope is limited. Satellite -based systems, especially those that are light and affordable, could climb worldwide.
But the current system is not perfect. Jinan-1 does not use tangled photons, which would allow even safer communication where not even the satellite knows the key. If the satellite were pirate, the key could be compromised. “The miniaturization of technology for tangle is more difficult,” PAN admitted, but said it is “completely feasible” in the future.
What follows?
This research offers a template for a future in which small satellite fleets cross in the sky, transmitting quantum keys to users as casually as GPS signals. The team is already planning to expand, launching multiple microsatellites and implementing more portable terrestrial stations.
They are also considering updates such as QKD sources based on photonic chips, daytime communication and integration with existing Internet satellites. These would enable 24/7 coverage and global reach.
If you succeed, they will not only be governments that encidential messages. Any person, from banks to hospitals and journalists, could one day plug at a quantum security channel as easily as opening a safe web page.
The findings appeared in the magazine Nature.
#Small #Chinese #satellite #quantum #messages #kilometers #hack #space #quantum #Internet #corner
