Chinese Breakthroughs Bring Quantum Tools Closer to Practicality

A tenfold leap in a key aspect of quantum communications is just one of several recent breakthroughs by Chinese research teams that have major implications for the future of computing and communications.

Quantum communications systems pass information using quantum bits: particles that exist in two states until they are observed. If an enemy observes these qubits—that is, intercepts a message—they lose this quality of “superposition.” The information they carry is lost and, as a bonus, the interception is easily detected. (Imagine dipping a cup into a stream of water; any attempt leaves traces.) But the intended recipients can interpret the information because they are being sent something called quantum keys. The inability to send enough of these keys has been a bottleneck in the pursuit of practical quantum communications.

Now a team of Chinese scientists at the University of Science and Technology of China has reported a breakthrough: a tenfold increase in the rate of stable quantum-key distribution. Led by the decorated USTC researcher Pan Jianwei and MIT-trained Xu Feihu, the team managed to push 115.8 megabytes of encrypted data per second over a 10-kilometer fiber-optic channel, shattering by over ten times the previous record of around 10 Mb/s. This breakthrough enables systems to handle vastly more data, larger files, and more users.

Another challenge for quantum systems, though, is that any increase in distance or bandwidth begins to introduce a large quantity of errors and decoherence. This is a result of the delicate superposition of the qubits, which frequently introduces unacceptable error rates and computational bottlenecking. Although these errors can be corrected by using extra qubits, this takes more computing power. It can even introduce more errors; the correcting qubits themselves are also delicate.

However, another Chinese team, led by Yu Dapeng of the Shenzhen Institute of Quantum Science and Engineering as well as researchers from Tsinghua and Fuzhou Universities, are also making progress on this problem. In March, the team announced a new system for real-time error correction in quantum systems. Their approach corrects for the added error potential of the extra qubits, improves the stability of information storage, and requires fewer resources, allowing quantum systems to realize a net-positive for resource intensity.

Beyond quantum communications

These breakthroughs come as a result of a broader push by Beijing for supremacy in quantum technologies and the many national security applications they promise even beyond the holy grail of communications that would reveal any attempted hack. Quantum computers able to solve complex calculations in milliseconds that would take a conventional computers trillions of years to solve would effortlessly crack most current encryption, push forward machine learning and AI to new levels, enable complex simulations and predictions, and drastically scientific R&D in fields ranging from chemistry to synthetic biology.

The PLA's interest in such areas and the quantum work at the University of Science and Technology of China dates as far back as 2012, when the university signed a strategic cooperation agreement with the PLA’s National University of Defense Technology regarding quantum computing research. The signing ceremony was attended by both the aforementioned Pan Jianwei, and Major General Yang Xuejun. The University also has a cooperation agreement with AVIC, China’s state-owned mega-conglomerate that produces platforms for the PLA Air Force, as well agreements with Yale, Cambridge, and other international organizations.

According to estimates from Global Quantum Intelligence, the Chinese government has likely spent at least $25 billion in the field. Much goes to quantum laboratories, according to a 2022 report from the RAND Corporation: $1.06 billion in 2017 and an additional $2.95 billion through 2022. The Chinese government has also funded private businesses. Pan Jianwei, team-lead for the quantum communications breakthrough, founded the quantum technology company QuantumCtek in 2009. In 2020, the company received funding from the state-owned China Telecom to establish quantum-encrypted communication lines in 15 Chinese provinces. 

These investments are now paying off. In addition to the above gains, China has also led massive breakthroughs in supercooled and light-based quantum processors.

Don’t panic

Still, concerns of a Chinese “quantum supremacy” should be softened by the realities and difficulties of this new space. For example, the NSA has noted five technical hurdles to applying quantum cryptography on the U.S. national security system. First, while quantum cryptography does prevent eavesdropping, there is no way of authenticating the sender of the secure information. Second, quantum communications require specialized equipment that cannot be integrated into existing infrastructure and cannot be upgraded or patched. Third, the trusted nature of the encrypted information means insider threats will become much more valuable to malicious actors. Fourth, tolerance for error is extremely low with the delicate qubits and quantum communications equipment. Five, this sensitivity makes denial-of-service attacks on quantum communications systems are much more effective than on traditional communications networks.

Perhaps most importantly, the NSA poured some cold water on quantum code-breaking. Although quantum computers will be able to crack most encryption, it will not be able to break all. “Quantum-resistant algorithms” can survive attempts by quantum computers to solve their codes, and are much cheaper to deploy to current systems than a complete redesign of security communications infrastructure. Their deployment is currently spearheaded by the National Institute of Standards and Technology, which announced the first group of winners of its quantum-resistant cryptographic competition last year.

Thus, although the new era of quantum computing, cryptography, and communications may bring some major changes, they are still a long way from being fully realized. Still, the spate of recent breakthroughs from Chinese scientists represent both major achievements and further signs that the road to the quantum age may well run through Beijing.

Thomas Corbett is a research analyst with BluePath Labs. His areas of focus include Chinese foreign relations, emerging technology, and Indo-Pacific security studies.