China's quantum satellite enables first totally secure long-range messages
Andrey VP / Shutterstock
In the middle of the night, the Micius satellite sends light particles to Earth to establish the most secure communication link in the world. It is invisible to anyone except special telescopes in two Chinese observatories. Micius, named after the ancient Chinese philosopher also known as Mozi, is the world's first quantum communications satellite and has been a leader in quantum encryption for several years. Scientists have now reported that they have reached an important milestone with this technology: long-distance, secure communication that you can trust without trusting the satellite through which it is traveling.
Micius was founded in 2016 and has achieved a number of breakthroughs under its operational team led by Pan Jian-Wei, China's “father of quantum”. The satellite serves as a source for pairs of entangled photons, twin light particles whose properties remain interwoven regardless of their distance. If you manipulate one of the photons, the other will be affected in a similar way at the same moment.
It is this property that lies at the heart of the safest forms of quantum cryptography, the entanglement-based quantum key distribution. If you use one of the entangled particles to create a key to encode messages, only the person with the other particle can decode them.
Micius previously generated entangled photons and delivered them via special telescopes to two ground stations (observatories) at a distance of 1,200 km. Scientists showed that the photons reach the Earth as intricately as in orbit.
Then, in 2017, the Micius team used entangled photos to encrypt transmissions that enabled a virtual meeting between the Austrian and Chinese science academies in Vienna and Beijing, respectively, at a distance of 7,400 km. This included the development of the key distribution machinery and a mechanism to prevent malicious attacks, such as blinding the telescopes with other light signals.
None of the communications went through Micius. Only the encryption keys were created and distributed. However, both ground stations had to speak to and trust Micius as part of their communication systems and use it as a relay before they could connect to each other.
Quantum encryption is based on entangled light particles. Jurik Peter / Shutterstock
A new paper from Pan Jia-Wei's laboratory, published in Nature, shows that Micius has successfully brought tangled quantum cryptography back to its original ground stations 1,200 km away. This time, however, the satellite simultaneously sent entangled photons to the ground stations to establish a direct connection between the two.
This gave them robust, unbreakable cryptographic protection without having to trust the satellite. So far, this had never been done by satellite or at such great distances.
Again, none of the messages went through Micius. The satellite provided entangled photons as a convenient resource for quantum cryptography, and the two ground stations then used them according to their agreed protocol. The new paper does not specify how the messages were transmitted in this case, but theoretically this could be done over fiber, another communications satellite, radio or other method that they agree on.
Secure long-distance connections like this form the basis for the quantum Internet, the future global network with additional security, which is driven by laws of quantum mechanics and cannot be reached with classic cryptographic methods.
The launch of Micius and the records that scientists and engineers used to help build quantum communication systems were compared to the impact Sputnik had on the space race in the 20th century. Similarly, the quantum race has political and military implications that are difficult to ignore.
Pan Jian-Wei attributed to Edward Snowden's disclosure of Internet surveillance by Western governments in 2013 that he had caused China to advance quantum cryptography research to create more secure means of communication. As a result, Micius was named Sputnik for the ultra-paranoid.
In theory, every country could rely on Micius to provide entangled photons to secure its communication. But the satellite is a strategic resource that other countries are likely to want to replicate, just like Europe, Russia, and China now have their own versions of the US-controlled GPS. However, the news of a successful quantum communication link over long distances is a sign that we are already living in a new era of communication security.
This article is republished by The Conversation under a Creative Commons license. Read the original article.
Harun Šiljak does not work for companies or organizations that would benefit from this article and has not disclosed any relevant affiliations that go beyond her academic appointment.
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