The podium is decorated with pink and white plastic flowers. The Chinese man behind it speaks at length about a laser radar system for detecting stealth aircraft. Amid the COVID-19 lockdown in 2020, his audience joins him virtually for the talk.

A young participant is curious — why is quantum research so important for Xinjiang? The Xinjiang Association of Science and Technology has organized the online session to showcase groundbreaking achievements in Chinese quantum research.

It's a "battlefield against terrorism," the lecturer replies, referring to the northwest province. As the technical director of Chinese start-up Quantum CTek's Xinjiang branch, his words are deliberate, even telling.

Securing the information sphere is the "the great challenge of our country's defense," the Quantum CTek representative says, as he accuses "hostile forces in the West" of trying to undermine China "by digging up and stealing our internal information".

Indeed, there have been major data leaks from the region, like the Xinjiang Police Files and the China Cables, that have revealed the scope of China's persecution and ubiquitous surveillance of its Uyghur Muslim minority.

The solution to this problem, the technical director of Quantum CTek's Xinjiang branch concludes, lies in achieving technological superiority by developing unbreakable quantum communication. That would support "the overall goal of a stable and lasting security for our society," he says, almost profoundly.

But how does all of this relate to Heidelberg?

DW and German investigative newsroom CORRECTIV trace the history of a quantum partnership spanning two decades — in a field of science with the potential to erode human rights and change the tide of conflict between superpowers. 

It involves the Physics Department of the venerable Heidelberg University and its honorary professor Pan Jian-Wei, who co-founded the quantum start-up Quantum CTek shortly after his return from Germany.

Hello, Heidelberg

In idyllic Heidelberg, the past and future collide. The southwestern city is home to Germany's oldest university, established in 1386. Today, it is amongst the country's top institutions of higher education. 

Its Institute of Physics is particularly renowned for its fundamental research in quantum physics and has attracted premier scientists from across the globe, including Chinese physicist Pan Jian-Wei.

Pan launched his studies in the 1990s at China's prestigious University of Science and Technology (USTC) in Hefei, but Europe offered him a unique chance to further explore frontiers in one of quantum's most advanced fields of application: quantum communication.

Emerging quantum technologies are forecast to have a major impact on all aspects of human life, including how wars are fought in the future.

"I firmly believe that these emerging technologies will ultimately bring broad benefits to human society," Pan tells DW and CORRECTIV in a long, written statement.

By 2003, the talented young scientist had moved to Heidelberg University after completing his doctoral studies in Vienna under the guidance of Anton Zeilinger, a star physicist who would later receive the Nobel Prize in Physics.

Quantum passions

Pan's fundamental research question concerned the feasibility of secure, unbreakable communication across varying distances. His research in Heidelberg was bestowed with major prizes and millions of euros in funding.

"Pan always possessed an unwavering curiosity towards fundamental questions and their potential implications for technological advancements," says Jörg Schmiedmayer, a former colleague at Heidelberg University.

Over a period of five years, Pan built up his research group undisturbed. Throughout this time, he often traveled back home to teach at USTC and to recruit promising Chinese quantum researchers for his lab in Heidelberg, where they also received financial support.

Pan's arrival in Heidelberg coincided with Europe's burgeoning interest in China. Back then, China was increasingly sought out as a major trading partner, particularly by Germany. Scientific collaboration was politically and economically desired.

"We spent five, six years together researching really cool fundamental things," says former colleague Schmiedmayer, stressing that the collaboration "had quite a decent impact."

With Pan at its side, Heidelberg's Institute of Physics grew in prominence, its reputation reaching new heights globally.

New horizons

In 2008, however, Pan decided to return to China and make USTC his home research institution, bringing not only several of his Chinese students with him, but also transferring his lab equipment and projects from Heidelberg to the bustling Chinese city of Hefei.

He managed to move the lab despite his research group receiving €1.4 million ($1.5 million) in additional project funding that year from the European Union.

Since his homecoming, China has regularly announced breakthroughs in the field of quantum communication.

In 2016, for example, Pan and his team launched the world's first quantum satellite into space. In the fall of 2017, they used the Micius satellite to establish the first tap-proof video conference between Beijing and Vienna.

Partnerships and rivalries

Pan's return to China did not harm his scientific cooperation with Heidelberg University, as documents obtained by DW and CORRECTIV show.

In 2009, Heidelberg University appointed him an honorary professor. USTC continued to send talent. In 2011, the two universities signed an official contract for the exchange of students and teaching staff. 

The years passed with fruitful collaborations.

By 2016, plans were made to set up a joint, cutting-edge quantum research center in China headed by Pan and his German colleague Matthias Weidemüller.

In the preamble to the contract, which was signed in 2017, a striking name was included — the National University of Defense Technology (NUDT). It is China's top military university and reports directly to the Central Military Commission, which is led by President Xi Jinping.

Heidelberg University told DW and CORRECTIV in a written statement that the NUDT played "no role" during the planning phase despite its name being included in the document. 

Such connections with a military institution would have "certainly been examined more closely at a later stage," the university added. However, it also acknowledged that the institution "would not enter into such an agreement today."

In fact, the joint quantum center has not been realized — and likely won't, in part, because of political pressure.

Today, China, a once coveted partner, has been dubbed a "systemic rival" by the EU and the United States, exhibiting an increasingly interventionist approach to global and regional affairs. Behind closed doors, the German government is bitterly debating a new China strategy whose publication is long overdue. 

In an early draft leaked last November, Germany's Foreign Office argued that China's policy of civil-military fusion "imposes restrictions" on scientific collaboration "in cases where it enhances China's ability to project military power externally or enforce repression internally."

A German physicist in China

On a warm, windy day in May, quantum physicist Matthias Weidemüller welcomes reporters from DW and CORRECTIV for an interview and guides them into a laboratory. He is eager to demonstrate the basic research conducted there, basic research being a term used by scientists to refer to experimental or theoretical work done primarily to acquire new knowledge.

Coincidentally, he joined Heidelberg's Institute of Physics the same year Pan departed. Despite that, he has assumed a major role in the international partnership.

Weidemüller prefers to "quietly crumble away" in his work. Scientists like him, he says, working on fundamental research, focus solely on advancing the field through experiments without any practical applications in mind. Yet, he also believes certain rules must be adhered to, and "that includes transparency, that includes public involvement."

The professor responds with confidence when questioned about his personal involvement with China. In 2013, he was presented with an opportunity to join USTC under Beijing's contentious "Thousand Talents Program," which seeks out pioneering scientists to conduct research in the country.

"What intrigued me was actually having the opportunity to witness firsthand how science, specifically quantum physics, works on site," says Weidemüller, who enthusiastically embraced the opportunity.

Other Western scientists have declined such offers, at times expressing concerns about academic freedom and national security.

His appointment ceremony at USTC was presided over by Pan, who remains grateful for the openness he experienced in Heidelberg.

"Promoting academic exchange and training talent across national borders and cultural differences is crucial to the healthy development of science, as it has a profound impact on the well-being of humanity," Pan writes to DW and CORRECTIV.

Between the lines

Under the Thousand Talents Program, Weidemüller established his own lab at the Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) located at USTC's secondary campus in Shanghai. 

Since his five-year part-time contract expired, Weidemüller has stayed on and was even named an honorary professor. He dedicated approximately two months each year to his work there until that rhythm was interrupted by the COVID-19 pandemic.

Weidemüller emphasizes that he set clear boundaries for himself and maintained academic independence over his research. "Nobody tells me what to do," he stresses repeatedly; all findings were publicly available while his laboratory remained accessible to all.

"The way you conduct your research allows you to decide the proximity or distance to practical applications," says Weidemüller.

Alongside Pan, USTC currently hosts eleven other Chinese quantum researchers who have returned from Heidelberg. They are actively involved in leading national quantum research initiatives. Some are participating in quantum-oriented technology startups with ties to defense companies.

Xinjiang links

Pan himself cofounded Quantum CTek shortly after his own return from Heidelberg and remains its second largest shareholder after USTC. The startup promotes itself with the slogan, "Quantum secures every bit." Domestically, the company calls itself Guodun Quantum, of which the first word translates to "national shield."

In a June 2022 report submitted to the Shanghai Stock Exchange, Quantum CTek listed its involvement in "several military projects." Apart from its main headquarters in Hefei — where USTC's main campus is located — the company maintains six additional locations, including the branch in Xinjiang that was established in 2017.

Pan, in his written response to DW and CORRECTIV, expressed a lack of knowledge regarding the presence of a Quantum CTek branch in Xinjiang. 

"After the early period of founding the company and implementing the technology transfer, I have no longer been involved in managing the company since 2011, except for being a shareholder," he says.

Setting up shop in such a highly militarized region, of all places, is certainly "no coincidence," says Yangyang Cheng, a Chinese-born particle physicist who studied at USTC. Cheng has lived in the US for more than 10 years, where she is a fellow at Yale Law School's Paul Tsai China Center.

"The fact that a company that is so new can open a branch there suggests that there are very, very close contacts with the Chinese security state," she adds.

Quantum CTek did not respond to multiple requests for information.

Imposing sanctions

In 2019, a report by US security company Strider revealed that Pan maintains extensive research contacts with the Chinese defense sector, effectively exploiting his German research ties.

"Heidelberg University is arguably the most important foreign partner behind China's rapid progress in dual-use quantum technologies," according to the report.

In November 2021, the US put Quantum CTek on its entity list as one of several Chinese technology companies that "support the military modernization of the People's Liberation Army and/or acquire and attempt to acquire US origin-items in support of military applications."

Despite multiple inquiries, US authorities did not provide further information.

Alongside Quantum CTek, USTC's HFNL laboratory, where Weidemüller conducted his research, has also been subject to US sanctions.

"One cannot remain indifferent to this," he asserts, "it would be naive to not be concerned."

Following the imposition of sanctions, the NATO Supreme Allied Commander Transformation, responsible for preparing the alliance for future warfare, was also briefed about the connections between USTC and Germany's oldest university.

An hour-long online presentation in February 2022 focused on China's quantum leap, along with USTC's longstanding partnership with Heidelberg University. Quantum CTek and major Chinese defense contractors, such as the China Electronics Technology Corporation (CETC), also featured during the briefing, DW and CORRECTIV learned from sources.

CETC dubs itself "the most powerful national central corporation in the fields of defense electronics [and] security electronics". Notably, it developed the police app used in Xinjiang for the extensive surveillance of Muslim Uyghurs.

A network emerges whose partners complement each other: In the spring of 2018, USTC and CETC entered into a scientific cooperation agreement — Pan signed on behalf of his university. CETC is also a major partner of Quantum CTek.

Pan explicitly states that, since his return from Germany, none of his projects have received any form of military support. However, in his written response to DW and CORRECTIV, he also stresses that "the development of any technology may be applied to military purposes."

He emphasizes the most crucial word of his core argument by capitalizing it: "Even though certain technologies might have military uses, it's not something that ANY scientist can control or predict." 

"What really matters," he adds, "is that I'm committed to advancing knowledge and creativity to help people and society as best as possible."

The limits of academic freedom

In 2021, the EU rolled out more stringent research guidelines in fields with high technological development.

As a result, Heidelberg University set up an export control unit in early 2022. This unit now assumes responsibility for scrutinizing all international research projects for their potential dual-use applications.

As governments across Europe struggle with defining relations with Beijing, Heidelberg University is also grappling with a fundamental question: Can scientific cooperation work when partners "have a proximity to military facilities that they may find hard to avoid because of the system?"

Anja Senz, a China researcher and — like Matthias Weidemüller — a member of Heidelberg's rectorate, is among those tasked with finding an answer.

The relationship with USTC is "a great case study for learning how things can actually develop," Senz says. She does not want to "define red lines per se," yet she thinks it necessary to critically reflect on "technological implications."

When asked about Pan, Senz emphasizes the need to carefully observe an individual's career. "At some point, one must also ask oneself: What role does this person play in this system?"

Weidemüller dodges direct questions about Pan. He opposes bluntly severing ties with USTC, even at the risk of joint basic research "somehow growing into something at some point through someone else."

"Should we simply cease global exchanges about nature's fundamental questions?" he asks candidly.

There is no easy answer — but what is certain is that China aims to have the most advanced army in the world by 2049, and quantum technology plays a crucial role in its plans. 

The country's quantum physicists are tasked with transforming "achievements in basic civilian research into military applications" — a task highlighted in a key strategic document for China's modernization, the 13th Five-Year Plan for the "civil-military fusion of science and technology."

Teri Schultz, Li Shitao and a colleague who does not wish to be named for security reasons contributed reporting.

Edited by Lewis Sanders.