More than a decade ago, Chinese physicist Pan Jian-Wei returned home from Europe to help oversee research into some of the most important technology of the 21st century.

At a conference in Shanghai this summer, Mr Pan and his team offered a rare peek at the work he described as a "revolution."

They spoke of the hacking-resistant communications networks they are building across China, the sensors they are designing to see through smog and around corners, and the prototype computers that may someday smash the computational power of any existing machine.

All the gear is based on quantum technology - an emerging field that could transform information processing and confer big economic and national-security advantages to countries that dominate it.

To the dismay of some scientists and officials in the United States, China's formidable investment is helping it catch up with Western research in the field and, in a few areas, pull ahead.

Inside Huawei's new campus for workers in China Show all 20 1 /20 Inside Huawei's new campus for workers in China Inside Huawei's new campus for workers in China An employee enters a train in the Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China A worker cleans a waterway as office buildings are seen at Huawei's new Ox Horn Research and Development campus in Dongguan, near shenzen Getty Inside Huawei's new campus for workers in China An area of Huawei's Ox Horn campus modelled after Cesky Krumlov in Czech Republic Getty Inside Huawei's new campus for workers in China The real Cesky Krumlov in Czech Republic Getty Inside Huawei's new campus for workers in China Employees sleep in their cubicle in the research and development area after lunch at the Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China An area of Huawei's Ox Horn campus modelled after Heidelberg in Germany Getty Images Inside Huawei's new campus for workers in China Employees play basketball on a court within the staff housing complex at the end of the workday at the Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China A replica of the Karl Theodor Bridge in Huawei's Ox Horn campus Getty Inside Huawei's new campus for workers in China The real Karl Theodor Bridge in Heidelberg, Germany Getty Inside Huawei's new campus for workers in China Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China Employees ride the bus home at the end of the workday from the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China Huawei workers eat their subsidised lunch in one of many large cafeterias at the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China Reception staff walk in front of a large screen showcasing different technologies in the foyer of a building used for high profile customer visits at the campus in Shenzen Getty Inside Huawei's new campus for workers in China An employee reads in the staff library on a break at the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China An area of Huawei's new Ox Horn campus modelled after a European City Getty Inside Huawei's new campus for workers in China Servers are seen inside Huawei's factory campus in Dongguan Reuters Inside Huawei's new campus for workers in China The conductor waits for a train in the Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China A general view shows the research and development centre at Huawei's Ox Horn campus AFP/Getty Inside Huawei's new campus for workers in China Employees works on a mobile phone production line at Huawei's factory campus in Dongguan Reuters Inside Huawei's new campus for workers in China An office building on the Huawei campus in Dongguan AFP/Getty

Beijing is pouring billions into research and development and is offering Chinese scientists big perks to return home from Western labs. China's drive has sparked calls for more R&D funding in the United States, and helped trigger concerns in the Trump administration that some types of scientific collaboration with China may be aiding the People's Liberation Army and hurting US interests.

"The United States must be prepared for a future in which its traditional technological predominance faces new, perhaps unprecedented challenges," the Centre for a New American Security wrote in a recent report about China's quantum ambitions.

Quantum technology seeks to harness the distinct properties of atoms, photons and electrons to build more powerful tools for processing information.

Last year, China had nearly twice as many patent filings as the United States for quantum technology overall, a category that includes communications and cryptology devices, according to market research firm Patinformatics.

The United States, though, leads the world in patents relating to the most prized segment of the field - quantum computers - thanks to heavy investment by IBM, Google, Microsoft and others.

Helping oversee China's programme is Mr Pan, whom Chinese media call the "father of quantum." From his labs at the University of Science and Technology of China (USTC), in Shanghai and Hefei, the 49-year-old leads a team of 130 researchers. In 2017, the journal Nature named him one of "ten people who mattered this year," saying he had "lit a fire under the country's efforts in quantum technology."

Mr Pan occasionally gives lab tours to President Xi Jinping, who takes a keen interest in his work, according to Chinese media. Mr Pan is also overseeing plans for a new national lab for quantum research in Anhui province, which he said had drawn about $400m (£330m) in government funding.

At the Shanghai event, Mr Pan illustrated his slide presentation with science-nerd jokes about Einstein and Star Trek. In a nod to Schrödinger's cat - a 1930s thought experiment that helped define a quantum concept called superposition – Mr Pan used images of a cartoon feline standing upright and lying flat on its back.

"As we all know, in our everyday life, a cat can only either be in an alive or dead state," Mr Pan said, but "a cat in the quantum world can be in a coherent superposition of alive and dead states."

He was making the point that quantum particles, also known as quantum bits, differ fundamentally from the bits in today's technology. Existing computers and communications networks store, process and transmit information by breaking it down into long streams of bits, which are typically electrical or optical pulses representing a zero or one.

Quantum bits, or qubits, which are often atoms, electrons or photons, can exist as zeros and ones at the same time, or in any position between, a flexibility that allows them to process information in new ways. Some physicists compare them to a spinning coin that is simultaneously in a heads and tails state.

In his talk, Mr Pan detailed how China is harnessing qubits to safeguard its communications from hacking - one of the fields in which China appears to have a lead over the West.

Mr Pan and his team are aiming to launch a constellation of satellites and a nationwide fibre-optic network that use qubits to securely transmit information. An almost 1,300-mile fibre link connecting Beijing, Shanghai and other cities is already up and running. So is a satellite China launched in 2016, which has conducted several prominent experiments, including facilitating a hacking-resistant video conference between Beijing and Vienna.

When the network is complete, it could complicate US efforts to eavesdrop on China's government or military communications, some Western scientists say.

"I predict China will go black in two to three years - we won't be able to read anything," said Jonathan Dowling, a physics professor at Louisiana State University who spends part of the year as a visiting faculty member at USTC in Shanghai.

Others argue that even if China's network equipment is more secure, it could still be hacked by manipulating the humans running the system.

If the technology gains traction globally, China could be in a strong position to sell it, given the large number of patents its universities and companies have registered for devices and technology relating to quantum communication and encryption, according to Patinformatics.

Mr Pan has credited Edward Snowden for motivating China's quantum research. The former National Security Agency contractor's revelations about NSA eavesdropping led China to pour money into developing more secure communications, Mr Pan has said in published interviews.

Barry Sanders, a Canadian physicist from the University of Calgary, spends two to three months a year as a visiting professor at the USTC labs in Shanghai. He got the job through China's "Thousand Talents" programme, which recruits Western scientists for teaching and research stints, and offers incentives to persuade Chinese researchers to return home from overseas.

Mr Sanders said China's cultural differences can provide advantages in the lab.

"I have my Western way of doing things - freedom of thought, take risks," he said. In China, there is more emphasis on the common good, he said. "One guy spent two years really focused on how to prepare the lab room. You can assign people these tasks - they will do something that in our world would be seen as beneath us. But here they are supported and held in high esteem."

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Mr Pan received his doctorate from the University of Vienna in 1999 and conducted further research at the University of Heidelberg before moving home, along with several Chinese colleagues.

China's work on quantum technologies at the time was "relatively backwards" and needed outside help, Mr Pan said in an email. "Therefore, our team took the initiative to send students to top research groups abroad to learn related technologies," he said. "Fortunately, they later returned back to work in China."

Most of the Chinese researchers speaking at the Shanghai conference spent years studying overseas. Their slide decks were peppered with humorous references to Western pop culture and events. One featured a picture of Donald Trump with the caption "Make SPDC Great Again" - a reference to an optical process whereby a photon splits in two. During a coffee break, one Chinese researcher's phone erupted in a ringtone from the TV show Friends.

Their PhDs or postdoctoral credentials came from universities such as Stanford, the Massachusetts Institute of Technology, Cambridge and the University of Toronto, according to their biographies printed in the programme.

While their talks did not focus on military applications, much of the technology they are pursuing would have clear uses in both the commercial and defences realms, scientists say.

Quantum computers might someday be able to crack all existing forms of encryption. Quantum sensors could help the Chinese military track and target enemy troops with greater precision. The university where Mr Pan works, USTC, has established several quantum-research partnerships with state-owned defence companies in recent years, with aims that include enhancing the combat capability of naval vessels, according to Chinese media reports cited in the Centre for a New American Security paper.

"China's national advances in quantum communications and computing . . . will be leveraged to support military purposes," according to the paper's authors, Elsa Kania and John Costello, who reviewed hundreds of Chinese-language media, government and technical reports.

Scientists who have discussed the field with US government officials say the Trump administration has recently expressed concern about the number of Chinese students pursuing studies in the United States in sensitive areas such as quantum science.

"We've always encouraged the best and brightest to come from overseas, and it's always served our nation well," said John Preskill, the Richard P Feynman Professor of Theoretical Physics at the California Institute of Technology, who has advised the government on quantum-tech issues. "But there is concern in government about how we are training all these people, and a lot of them are going back to China and competing in technologies that have implications for national security. And we're talking about what to do about it.”

Mr Preskill added: “Many of us in academia, although we know there are complicated issues, are inclined to continue encouraging Chinese students to come.

“But there is a continuing discussion in the government about what's the best policy for doing that.”

In an opinion piece this month, two US university associations said their members were strengthening security protocols and building closer relationships with the FBI and intelligence agencies, after hearing "increasing concern" from the federal government about "foreign interference" in university research. They also praised the contributions of Chinese students and faculty, and said the United States must continue to welcome them.

Mr Pan said he believed collaboration would bring only rewards in quantum science.

"The academic exchange benefits both countries," he said via email. "I see no reason whatsoever that the United States government should be concerned and discourage normal academic activities. Recall that quantum mechanics was first developed in Europe, and then moved to the United States."

Asked whether his group contributes to research for the Chinese military, Mr Pan said his university and team are "by nature, for fundamental scientific research and education."

"We publish our fundamental research results in international journals which are available to read from all around the world. From reading our papers, other people, who can be from the United States, Europe, Japan, or China, might be inspired and further develop 'immediately useful' technology or products for industry or commercial or military use," he said, adding this was "out of our control."

Some corners of the US government are restricting collaboration with China. In June, the Energy Department, one of the main agencies funding physics and quantum-science research, prohibited its employees and contractors from responding to certain foreign countries' talent-recruitment programmes, including China's Thousand Talents. The agency said it wanted to limit "unauthorised transfers of scientific and technical information."

The ban followed the indictment of a former scientist at the Energy Department's Los Alamos National Laboratory on charges of making false statements about his involvement with Thousand Talents.

"What we have said in shorthand is, you cannot work for the Department of Energy and for one of these foreign talent recruitment programmes. You cannot work for a foreign country and the Department of Energy at the same time," Chris Fall, director of the agency's Office of Science, said in an interview.

In part motivated by China's progress, Congress late last year passed the National Quantum Initiative Act, which authorised an extra $1.2bn in research funding over five years. The Energy Department is on tap to receive a big chunk of that money, which it plans to use to set up several quantum-focused research centres. The agency is soliciting ideas from its own national laboratories and from universities and the private sector as it decides how to establish those centres, Mr Fall said.

"The beauty of how we do science in this country is that it isn't top-down," he said.

For now, China is lagging behind the US tech industry in perhaps the most important race in the field: building a quantum computer.

A fully functioning quantum computer has the potential to be transformative. The exponentially greater calculation power could help identify new chemical compounds to treat intractable diseases, and eliminate traffic snarls by predicting and managing the flow of vehicles.

However, the possibility that the machines could eventually crack all existing forms of encryption is a major worry for militaries, governments and businesses that handle sensitive data.

To get a fully functioning computer - a goal still a decade or more away, most scientists agree - researchers must coax a large number of qubits into working together efficiently. That's difficult because qubits are finicky and have the propensity to stop functioning at the slightest disturbance, such as a minor change in temperature.

Google and IBM are at the forefront, using superconducting circuits to manipulate qubits. Google last year unveiled a quantum processor with 72 qubits, surpassing IBM's previously announced 50-qubit computer.

More important than the number of qubits is how effectively they work together, said Chris Monroe, a University of Maryland physicist and co-founder of the start-up IonQ. The company recently reported that its prototype computer, using 11 qubits made of ionised atoms, performed more complex calculations with greater accuracy than any rival machine. (IonQ's investors include AWS, a subsidiary of Amazon, whose founder, Jeff Bezos, owns The Washington Post).

Chinese researchers so far have reported a 12-qubit processor, using superconducting technology similar to Google's and IBM's.

The leader of that work, USTC professor Zhu Xiaobo, presented his team's results at the Shanghai conference, flashing a picture of their prototype on the screen - a shiny tangle of coaxial cables resembling an intricate golden chandelier. (IBM's and Google's machines have a similar look.)

"We are now working on 24 qubits," Mr Zhu said. "We hope next year we will go to 50, and maybe sometime we will go to quantum supremacy," he added, referring to the point at which a quantum computer is able to perform a calculation that existing computers cannot. The benchmark, though widely anticipated, will mark only the beginning of progress in the field, scientists say.

Lu Chaoyang, a young physicist who earned his PhD at Cambridge University, also stepped to the lectern to deliver an update on his team's approach to quantum computing. It relies on photons, which he dubbed "fast-flying qubits."

Mr Lu, whom Mr Sanders calls a "rising superstar" in China, peppered his talk with funny cat GIFs and Western cultural references.

Although the idea for a quantum computer first surfaced 40 years ago, there is still a long way to go, Mr Lu said.

He then pressed play on a brief video snippet of Harry Potter author J K Rowling, who spoke about the importance of setting "achievable goals."

"It's important we set achievable goals for experiments so we can continuously progress," Mr Lu said.