麻豆传媒

QUANTUM computers and networks, once merely physicists鈥� playthings, are increasingly seen as both a national security threat and a potential asset, with the theoretical ability to crack current encryption methods, but also improve artificial intelligence. The , the US and Australia drew a lot of attention for its focus on nuclear-powered submarines, but this AUKUS deal also promised to share quantum technologies.

It makes sense for Australia and the UK to ally themselves with a quantum tech leader like the US, not least because China, the other leader in the field, seems to be pulling ahead. In recent months, Chinese researchers have published details of the world鈥檚 largest metropolitan quantum communication network and the nation鈥檚 second demonstration of quantum supremacy 鈥� the ability to solve a problem that is all but impossible for regular computers.

At the heart of the security threat is quantum computers鈥� potential use as a tool for finding the prime factors, or multiplicative building blocks, of a number 鈥� for example, the prime factors of 21 are 3 and 7. Modern encryption relies on the fact that, for large numbers, this task would take hundreds of years for even a powerful supercomputer to solve.

But in 1994, a physicist called Peter Shor came up with a theoretical quantum algorithm to find prime factors much faster 鈥� once the hardware is available to run it. Although quantum computers aren鈥檛 yet powerful enough to threaten encryption, it may not be long before this changes. When that happens, secret communications around the world will be laid open.

Quantum computers could also radically speed up the training of the neural networks that drive most of our artificial intelligence systems, providing a boost to algorithmic surveillance.

Because of this, governments want to be the first to have advanced quantum computers for use against other states, but also want robust quantum communication networks that are immune to Shor鈥檚 algorithm thanks to quantum cryptography.

The US 鈥渇aces a reckoning鈥� on this front and its technological might shouldn鈥檛 be taken for granted, , a think tank in Washington DC, told a .

鈥淭he belief was that China still lagged behind, perhaps by years, in quantum computing and that there still was some time before we see Chinese universities or enterprises going head-to-head with the likes of Google,鈥� said Kania, referring to the US firm that made the first ever demonstration of quantum supremacy in 2019. 鈥淚nstead, the gap appears to have been closer to months.鈥�

Kania pointed out that, as investment in quantum research has grown, transparency and US-China collaboration has diminished. Visas for Chinese students wishing to study in the US are harder to come by, she said, and those working on quantum projects often returned to China after studying. Meanwhile, few Western researchers are part of quantum teams in China.

Last year, the US government put $625 million into quantum technology research, following the National Quantum Initiative Act signed by the then President Donald Trump in 2018. That is an increase on other US government funding: a leak by Edward Snowden in 2014 revealed that the US National Security Agency had spent $80 million in 2011 trying to develop a 鈥渃ryptographically useful quantum computer鈥�.

These initiatives aside, it is generally US firms rather than the state that makes quantum advances: the aforementioned Google, along with Microsoft, Amazon, HP and IBM, are all working on quantum computing, albeit using different architectural approaches, as are defence firms like Raytheon, Northrop Grumman and Lockheed Martin.

In China, meanwhile, the state takes the lead, with the publicly funded University of Science and Technology of China (USTC) in Hefei as the epicentre. A new National Laboratory for Quantum Information Science was just constructed in the city at a .

In July, USTC announced it had surpassed Google鈥檚 quantum supremacy efforts by solving a problem three orders of magnitude harder than that performed by the US firm鈥檚 Sycamore computer. In September, it bested its own benchmark by another three orders of magnitude.

USTC is making great strides in quantum communication too. It recently revealed that the world鈥檚 largest metropolitan quantum network 鈥� involving banks, universities and government buildings across Hefei 鈥� has been running for nearly three years. In 2016, the university put the world鈥檚 first quantum satellite into orbit, which it used to demonstrate that it was possible to conduct secure communications with ground stations on Earth.

says USTC is well funded over a long time frame, which is key to success. 鈥淣one of this would work without having the confidence that you鈥檝e got sustained funding over a longer period to have a go at things at scale,鈥� he says.

Winning the race

So is China ahead in the quantum race? says that, while USTC is winning on the number of quantum bits, or qubits, in its computers (a rough measure of their power), Google is ahead on quality. So, although USTC has been publishing work showing it has developed more qubits, Google has been striving to bring its qubits closer to useful operation with improved error correction and accuracy, he says.

However, it is all to play for. The ultimate goal for groups researching qubits is to develop the transistor of the quantum computer world 鈥� the 鈥渂uilding block that鈥檚 so reliable that it just clobbers all of the competition鈥�, says Aaronson. Who will get there first is still unclear. 鈥淭here鈥檚 always an element of luck,鈥� he says. 鈥淭he truth is that, right now, no one really knows which of these approaches, if any, will be the right one for scaling up.鈥�

Crucially, Aaronson says that a greater diversity of approaches are being tried in the US than in China. USTC, like Google, is heavily invested in superconducting qubits. But while IBM is also working on superconductors, Microsoft is aiming to use a type of quasiparticle that .

鈥淚f all the top people were being vacuumed up into a secret quantum computing programme, we鈥檇 notice鈥�

There are also claims that China鈥檚 budget isn鈥檛 what it at first seems. has promised $10 billion for quantum research, but that investment has yet to arrive, so teams have been operating with money from local government. When central funding comes, it is likely to only total around $1 billion, he claims. China鈥檚 central government didn鈥檛 respond to a request for comment.

鈥淲e have been pushing this, but the real money has not arrived yet,鈥� says Lu. 鈥淲e鈥檝e done all this work even without the national big budget. I think Google alone maybe will have more than we invest for the whole country.鈥� Google didn鈥檛 respond to a request for comment, but is reported to be planning to spend .

鈥淲e鈥檙e not moving so fast in terms of the national project because not all scientists in China are convinced. We鈥檙e still waiting for the real money. If there鈥檚 a further delay, we鈥檒l definitely be left behind,鈥� says Lu.

Whichever country first achieves large-scale quantum computing will undoubtedly have an advantage. But it may not be as dramatic as some fear, and the milestone is likely to arrive gradually rather than suddenly being revealed to the world.

鈥淚 can鈥檛 prove that if some intelligence agency right now wanted to spend a trillion dollars to build a scalable quantum computer and break encryption that they couldn鈥檛 do it, on a pretty fast timeline,鈥� says Aaronson, but 鈥渢here鈥檒l be some warning鈥�, he says.

First, researchers need to develop even a single reliable, error-corrected qubit, which has yet to be done. Then, this work would have to be scaled up to produce millions or billions of qubits. 鈥淵ou might fill an entire building,鈥� says Aaronson, meaning it is unlikely this is going on behind closed doors in a quantum version of the US Manhattan Project that developed nuclear weapons, he says.

鈥淨uantum computing is a pretty small community 鈥� we mostly all know each other 鈥� and if all the top people were being vacuumed up into some secret programme, we鈥檇 notice,鈥� says Aaronson.

In other words, although both US and Chinese teams have achieved quantum supremacy, the world is yet to see a quantum superpower 鈥� and perhaps, ultimately, there won鈥檛 be one. 鈥淨uantum computing is not a race between different countries, not a race between China and the United States. It鈥檚 a race between human beings and nature,鈥� says Lu. 鈥淲e would like to share with other scientists in the West and we would like to be a part of the whole science community.鈥�

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