“Switzerland could play a key role in quantum technology”

ETH Professor Klaus Ensslin spent 12 years at the helm of the National Centre of Competence in Research “Quantum Science and Technology”. As the programme prepares to wind down at the end of this year, we spoke to him about scientific breakthroughs and Switzerland’s role in quantum research.
Klaus Ensslin looks back with pride on the last 12 years, as researchers of the NCCR QSIT have been able to achieve important breakthroughs in many areas of quantum research. (Photograph: ETH Zurich/D-​PHYS/Heidi Hostettler)

Mr Ensslin, the National Centre of Competence in Research “Quantum Science and Technology” (NCCR QSIT) is now in its final month. It spanned a period shaped by the “second quantum revolution”. Could you explain what that is?
The “second quantum revolution” refers to the entanglement of quantum objects, a phenomenon that enables us to control multiple quantum systems. Developments in this field began in the 1980s and expanded in recent years to incorporate the aspect of engineering. In other words, it was no longer about just controlling multiple quantum objects, but also using them to build entirely new systems.

When was the first quantum revolution?
That started in the 1950s with the development of devices such as the laser and the transistor, which are also based on the principles of quantum mechanics. Back then, the focus was on finding technical applications for specific quantum-mechanical aspects. The difference today is that we’re using quantum objects to build things that didn’t previously exist. Take my colleague Tilman Esslinger, for example, who builds optical lattices and populates them with cold atoms in order to create completely new states. Or Yiwen Chu, who couples mechanical oscillators coherently to superconducting circuits. None of those things occur in nature.

Today’s quantum research involves all sorts of wildly different systems. Is this scatter-gun approach actually a useful way to meet long-term goals such as building a quantum computer? Or are we now starting to see researchers focusing on specific technologies?
At some point, quantum technology will hone in on specific fields, just like we’ve seen in other areas of technology. The big players have already made their choices: Microsoft has opted for topological qubits, while Google and IBM are working with superconducting circuits. But I think it will take at least another ten years to discover which technology is best. It’s even possible that we haven’t hit upon the best option yet, so it would be wrong to box ourselves in at this stage.

Looking back over the NCCR QSIT, what would you describe as its greatest achievements?
In scientific terms, we achieved milestones in most disciplines. At ETH Zurich, for example, we improved error correction in quantum systems and made advances in controlling ever-larger quantum objects. Our colleagues at the University of Geneva set a new world record by transmitting quantum-encrypted data over a distance of 550 kilometres. And researchers at the University of Basel managed to couple together two different quantum systems using optical fibres. These are the kinds of steps that will help us in future, because more and more of our work is likely to be with hybrid technologies. The fact that NCCR QSIT members managed to secure some 40 ERC grants was a huge success that gave our research an extra boost.

«The science is going so well and quantum research is a jewel in Switzerland’s crown, but it’s all been sacrificed. The consequences will become clear in a few years’ time. »      Klaus Ensslin

What’s the next step now that NCCR QSIT is coming to an end?
Under the leadership of Andreas Wallraff a new Quantum Center at ETH Zurich has been established, which will foster collaboration between the various academic departments. Similar centres exist in Basel, Geneva and Lausanne. On a national level, January 2023 will see the launch of the new Swiss Quantum Initiative, which will create a network of the various key players. All the participating universities agree that quantum research is a hot topic, as demonstrated by the EU’s decision to invest at least 1 billion euros in its Quantum Flagship back in 2018.

That’s exactly the kind of large-scale research programme from which Swiss researchers are now excluded.
In the first round of the Quantum Flagship, Switzerland received 25 million euros of research funding and was involved in 6 of the 20 projects. To put that in context, Germany secured 40 million euros and all the other countries received less. So Switzerland actually played a disproportionately large role. In the second round, none of us were eligible to take part. The Swiss National Science Foundation put up the funds for a replacement programme, but obviously it’s not the same.

Won’t the EU ultimately suffer by taking such a hardline stance?
I think it might, and the EU researchers would actually prefer to have us on board. But it’s no use! This is a clear case of science being held hostage to politics.

What does that feel like?
It’s painful. The science is going so well and quantum research is a jewel in Switzerland’s crown, but it’s all been sacrificed. The consequences will become clear in a few years’ time. As an established researcher, I can cope with them, because I’ve already built up my own network, but the consequences for young researchers will be really tough.

Another influencing factor is the role played by the tech giants who are investing huge sums in quantum research. Is that a stroke of luck for researchers?
The involvement of these big companies has various consequences for academic research. Some segments of our discipline have been flooded with money, and many good people have moved into industry as a result. One big company even poached an ETH physics professor, which is unusual. But the huge investments being made by the tech giants have also yielded new opportunities for collaboration, with all the advantages and disadvantages those entail.


The National Centre of Competence in Research “Quantum Science and Technology” (NCCR QSIT) was launched in 2011 and has been extended twice. ETH Zurich was appointed as leading house, with the University of Basel as co-leading house. Other participants in the NCCR QSIT include EPF Lausanne, the University of Geneva, the IBM Zurich Research Laboratory and the Università della Svizzera italiana in Lugano.

The NCCR QSIT brings together two of the 20th century’s key areas of research – quantum physics and information theory – as the basis for developing 21st-century technologies.

Can you be more specific?
Well, these collaborative ventures allow us to embark on technically complex projects that would otherwise be impossible. Big industry is a professional operation that is good at making rapid advances in individual areas. The flip side is that companies tend to frame their objectives in fairly narrow terms. They specify exactly where they want to be at a certain point in time, which reduces the scope and freedom of research work. In contrast, scientific advances in university settings gain much more visibility because there’s always the feeling that they could mark the next decisive breakthrough for the entire field.

As well as the tech giants, the US and China are also investing large sums in quantum research. Can Europe keep up?
Europe plays a leading role in fundamental research, so we certainly won’t be left behind there! What we’re lacking is big companies that are willing to take a gamble. On the plus side, we do have an IBM Research lab here in Zurich, which we’ve successfully collaborated with for years.

What role do the spin-off companies play that emerged from the NCCR QSIT?
A bigger role than many people realise. They may not generate billions in sales, but they’re highly innovative. Switzerland could potentially play a similar key role in quantum technology to the one it plays in the automotive industry. It may not produce any cars itself, but it’s home to many of the most important suppliers.

What’s the situation in regard to teaching, particularly the Master’s programme in Quantum Engineering that was launched in 2019?
ETH Zurich was the first university to launch that kind of degree programme, though similar courses have now been introduced in Lausanne and Geneva. So far, it’s been a very positive experience. The students are fantastic, and really motivated – that’s good news for everyone, because one of the biggest bottlenecks in quantum research is the lack of people with specialised skills.

What contribution has the NCCR QSIT made to promoting women?
The Department of Physics has made real progress in recent years and we’ve appointed a number of young female professors. The NCCR QSIT has benefited from the universities’ hiring policies, because far more women are now doing their doctoral project in quantum research. One of the key ways we’ve come up with for promoting women at NCCR QSIT is through the Inspire awards, which empower female scientists at the Master’s and postdoctoral level. These awards have now also been launched by other National Centres of Competence in Research and by the new Quantum Center at ETH Zurich. But, obviously, we need to strengthen our efforts towards an open and inclusive culture in quantum research.

Further information

Klaus Ensslin has been Professor of Experimental Physics at ETH Zurich’s Laboratory for Solid State Physics since October 1995. His research focuses on the electronic properties of novel semiconductor nanostructures. One of his group’s key goals is to achieve ever-increasing control of the quantum properties of electrons in nanostructures. Klaus Ensslin was co-initiator and director of the NCCR QSIT.