In November, the United States government added 12 more Chinese companies to its export blacklist, citing national security concerns. This time, quantum computing firms were among them. According to the US Commerce Department, some of the firms added to the blacklist aided the Chinese military’s “counter-stealth and counter-submarine applications, and the ability to break encryption or develop unbreakable encryption”. These are all applications that have been linked to quantum technology, which both the US and China are racing to develop. How exactly does this technology work, and is it really a game-changer? Read on to find out. What is quantum technology? Quantum technology is a complicated area of physics that explores the behaviour of subatomic particles – particles that are smaller than atoms, the basic building blocks of all matter. One major area of interest within quantum technology is quantum computing. Unlike a classic computer, which performs calculations one at a time, a quantum computer can perform many calculations at the same time. The basic unit of information in classic computing is a “bit”, which represents one of two binary values – either zero or one. The computer is able to interpret these values and represent them in various formats, including words and images. How China hopes to win the quantum technology race Quantum computers use a different basic memory unit: a qubit, which has the flexibility to represent either zero, one or both at the same time. This ability of an object to exist in more than one form at the same time is known as superposition. Things get more complicated when multiple qubits in the computer interact with each other. This is where the concept of entanglement comes in: multiple particles in a quantum system are connected and affect each other. For example, if one qubit represents zero, another qubit entangled with it will assume the value of one, and vice versa, making the measurement of each qubit dependent on the other. Because quantum computers’ basic information units can represent all possibilities at the same time, they are theoretically much faster and more powerful than the regular computers we are used to. Physicists in China, for instance, recently launched a quantum computer they said took 1 millisecond to perform a task that would take a conventional computer 30 trillion years. If they’re so great, why aren’t all computers quantum computers? Considering our obsession with speed in technology, you might think quantum computing would be the default by now. But so far, these machines work only in a protected environment for short periods on highly specific tasks, and they make a lot of mistakes. Hence, it is a matter of debate between scientists whether “quantum supremacy” – the idea that quantum computers could do better than their conventional counterparts, at least on some specific tasks – has ever been achieved. One big challenge for scientists is getting qubits to maintain superposition and entanglement long enough to complete a task. Quantum states of superposition and entanglement are extremely fragile and without the right temperature and environmental conditions, they lose their qualities quickly and behave erratically. New study reveals time can flow either way in quantum physics To function properly, qubits have to be stored in special refrigerators at ultra-low temperatures close to the point where atoms stop moving. The need for specialised equipment is a key reason only countries willing to invest a large amount of resources have studied quantum computing. Leading Chinese quantum physicist Pan Jianwei estimated in October it would take “four to five years of hard work” to correct quantum errors for two quantum computers his team developed, before they could look at solving important scientific questions with practical value. What are some potential applications? In an article published in 2020, Pan, the father of China’s quantum satellite programme, outlined three applications for quantum technology the country was trying to develop: Quantum sensors which could reveal a submarine hiding hundreds of metres under the ocean, or guiding devices that could operate independently for months without a GPS signal; Quantum computers , which could perform calculations that would take present-day high-performance computer thousands of years to solve – such as cracking encryption – in seconds; Quantum internet using entangled particles to transmit messages, leading to ultra-secure communications. Aside from military and national security applications, quantum research could help achieve important scientific breakthroughs. There are hopes that quantum computing could help researchers develop new drugs by modelling larger, more complex molecules a lot faster, according to a 2021 McKinsey report. Researchers are also studying climate applications, and propose that high-speed quantum computing simulations could help scientists create more efficient batteries or fertilisers, or find ways to optimise processes to reduce carbon emissions. As interest in quantum computing applications grows, tech giants at the front of R&D – including IBM, Google, Huawei Technologies Co. and the South China Morning Post ’s parent company Alibaba – have provided free platforms for people to develop quantum algorithms. Which countries are leading in the quantum technology race? Britain, the European Union and the US have all published plans in recent years to take a lead role in the global race on quantum science and technology. China’s national quantum programme, on the other hand, was shrouded in secrecy until 2020, when it listed quantum technology as a top priority, along with six other key science and tech areas in the country’s five-year development plan . In December 2021, a Harvard report said that in quantum computing, quantum communication and quantum sensing – three areas traditionally led by US researchers – “China is catching up and, in some cases, has already overtaken America”. Both countries have invested a huge amount of money and set out stringent policies related to the study of quantum technology. In September 2020, Pan and his team claimed to have achieved quantum supremacy with a new machine that was one million times faster than the record held by Sycamore , a quantum computer built by Google. China has more than 3,000 patents related to quantum technology, about twice as many as the US, but falls behind in terms of patents specific to quantum computing, according to a Valuenex report in 2021. Why is the US worried about China’s quantum research? According to a US congressional research report, quantum computing could be a threat to current encryption methods by around 2030-2040. Modern encryption used to protect information is nearly impossible for regular computers to crack, but quantum computers could do so with their superior processing power. This could allow “adversaries to gain access to sensitive information about US military or intelligence operations”, the report said. Elite Chinese school offers country’s first quantum tech PhD programme The report also predicted that with improvements in both quantum computing and machine learning, a subfield of artificial intelligence, countries could develop more accurate and deadly weapons. China has already developed quantum equipment with potential military applications. This year, scientists from Tsinghua University developed a quantum radar that could detect stealth aircraft by generating a small electromagnetic storm. In 2017, the Chinese Academy of Sciences also developed a quantum submarine detector that could spot submarines from far away.