Why quantum communication is leading technology?
Uncrackable quantum communication may be a step closer after Chinese researchers demonstrated a practical thanks to sharing security keys over 1,120 kilometers using entangled photons sent and received by satellites.
In 2017, a team lead by China’s Jian-Wei Pan broke new ground once they showed they might transmit pairs of entangled photons—particles tied together by the strange laws of quantum mechanics—from a satellite to 2 ground stations 1,200 kilometers apart.
At the time this was hailed as a serious step towards creating an ultra-secure channel supported “quantum key distribution,” where these entangled photons are wont to transmit a cryptographic key to 2 receivers which will then be wont to decrypt messages sent over a standard channel.
This approach relies on the very fact that manipulating or measuring the state of any quantum system changes it. meaning the receivers can tell if anyone is eavesdropping when the quantum key’s transmitted to them, making it essentially impossible to hack the channel without them realizing.
The only problem was that the complexity of firing photons from space through kilometers of atmosphere filled with clouds and mud to a telescope only a few of meters across meant that only about one photon out of six million sent from the satellite made it through, which is way too few to transmit a quantum key.
Now, though, Pan’s team has fine-tuned their approach, and during a paper published today in Nature, they describe how they sent a quantum key to 2 ground stations 1,120 kilometers apart. they need also hardened their quantum communication system against a spread of potential hacks that would sidestep the safety of the quantum keys.
The key to the breakthrough was a two-fold increase within the ground stations’ ability to gather entangled photons. This was achieved through a spread of tweaks to the telescope, including a replacement coating for its lens, and a series of optimizations of the optical systems wont to detect the entangled photons.
This resulted during a system that would securely transmit 0.12 bits per second. as long as the satellite can see both ground stations for 285 seconds each day, meaning that the satellite could transmit roughly 34 bits of knowledge during a sitting. That’s still not tons of knowledge, but definitely within the region required to deliver a practical quantum key.
The researchers estimate the link efficiency of the satellite-based approach system is 11 orders of magnitude above the choice approach for delivering quantum keys. That’s through optical fibers and has thus far only managed to realize distances of 100 kilometers.
On top of improving the efficiency, the team has tackled a number of the potential side-channel attacks that a hacker could use to compromise the secure link. A side-channel attack is one that doesn’t exploit weaknesses within the underlying cryptographic system, but instead, within the way it’s implemented in software and hardware.
In the system developed by the Chinese researchers, these include things like minute variations within the efficiency of various single-photon detectors, the very fact that these components don’t respond for a brief period after detecting a photon, or the way beam splitters respond differently to varied wavelengths of sunshine. All of those quirks could potentially be exploited by a hacker to undercut the safety of the system, but Pan’s team developed a spread of hardware tweaks to negate potential attacks.
The result’s a practical quantum key distribution system that’s ready to operate at distances over 1,000 kilometers, a big improvement over previous optical fiber-based solutions. Considering an equivalent team unveiled a mobile ground station earlier this year also as a way for connecting quantum memories over distances of up to 50 kilometers, it seems China is well ahead within the race for a quantum internet.