A new quantum key distribution method uses a quantum state with the potential to encode more than one bit per photon Image: iStock Photo
Chinese researchers have put forward a new quantum cryptography standard that could, if confirmed, substantially increase the speed of encrypted messages. The proposed new standard has been simulated on computers although not yet tested in the lab.
Quantum cryptography, the next-generation of secret messages whose secrecy is guaranteed by the laws of quantum mechanics, has been in the news recently. Last fall a group from the Chinese Academy of Sciences transmitted quantum cryptographically encoded communications (via satellite) to a ground station in Vienna, Austria.
The communications included quantum-encoded images and a 75-minute quantum-cryptographically secured videoconference, consisting of more than 2 gigabytes of data. IEEE Spectrum reported on the event at the time. And now, as of last month, the entire project has been detailed in the journal Physical Review Letters.
Media coverage of the event stressed its significance in moving toward a so-called quantum Internet. Yet the quantum internet would still be a distant dream when quantum cryptography can only mediate one or, at most, a few quantum-secured communications channels. To scale up to anything worthy of the name quantum Internet, quantum cryptography would need to generate not only thousands of cryptographic keys per second. Rather, a scalable quantum crypto system should aspire to key-generation rates closer to billions per second or greaterin the gigahertz (GHz) range and up, not kilohertz (kHz).
Theoretically we can get gigahertz levels of quantum key distribution, says Pei Zhang, professor of applied physics at Xian Jiaotong University in Xian, China.
Zhang and five other researchers from his university and Tsinghua University in Beijing have built a quantum crypto protocol on a different and potentially more capacious standard than what last falls video teleconference used. (To be fair, other GHz-speed quantum crypto protocols have recently been proposed as well.)
The teleconference, mediated by a dedicated quantum communications satellite China launched in August 2016, was secured by a kilohertz-speed quantum encoder that gener...