In recognition of the International Year of Quantum Science and Technology (IYQ) 2025, the UN Chronicle posed a series of questions to Professor Dr. Klaus Richter, President of the Deutsche Physikalische Gesellschaft (DPG)/German Physical Society, concerning the nature of quantum physics and its potential benefits for humanity. The resulting interview is aimed at providing our readers with accessible information on this highly complex field of scientific and technological development.
Interview
The International Year of Quantum Science and Technology (IYQ) aims to expand public understanding of quantum technologies, including their transformative potential. For our broad readership, could you explain what quantum mechanics is and why it matters?
Classical mechanics describes the macroscopic world around us, from the movement of the planets to billiard balls. However, it fails in the microcosm. Quantum mechanics is the theoretical framework behind quantum physics. It fills this gap on the smallest length scales and describes the behaviour and interaction of molecules, atoms and even smaller particles that make them up. In classical physics, energy varies continuously. In quantum physics, on the other hand, energy is limited to discrete values and grows in steps. Energy is hence a multiple of smallest “energy portions”, the quanta.
Quantum mechanics has impressively completed our view of the world and made the atomistic cosmos accessible to us: what began as a vague theory in 1925 allows us to understand nature: Why does the sun shine? What holds atoms together? Why do some molecules contribute to global warming and others don't? Why are things magnetic? All these everyday experiences can only be explained by quantum physics.
Moreover, quantum mechanics has led to revolutionary technical developments and is now an integral part of our everyday lives: Take transistors as building blocks of our smart technologies, such as computers and cell phones, LEDs (light-emitting diodes) as energy-saving light sources, positioning and navigation (GPS), the new definition of the kilogram, or magnetic resonance imaging as an important tool for medical diagnosis. Quantum mechanics has an impact on all areas of our science, technology, culture and art.
You have noted that that “after 100 successful years of quantum physics, we may be on the threshold of a second quantum revolution”. What do you think will be the next major impacts in our lives due to progress in quantum science and technology?
The “first quantum revolution”, building on energy quanta and the wave nature of quantum particles, began in the middle of the twentieth century. The “second quantum revolution” has started around the beginning of the twenty-first century. It is based on the rising ability to fully control the quantum behaviour of the elementary constituents such as photons or atoms. These achievements may pave the way we think about computing, measurement and information in the future. Some products of quantum technology, such as atomic clocks, are already at work; others, such as quantum computing, are going to pass from research to first commercial applications. With new quantum algorithms, quantum computers, one day, could tackle new, highly complex problems. Sophisticated methods of entanglement, another hallmark of the “second quantum revolution”, could lead to completely new sensor technology.
I think that there are no limits to creativity in the field of quantum applications. Future quantum technologies are presumably strongly influencing our world once again. But we simply do not know when and in what form this will happen in the distant future. Here, the evolutionary development of quantum technologies over the last 100 years may give us a clue: In the 1950s breakthroughs such as the laser or single-atom manipulation were simply not anticipated. We should have the fantasy to expect in our remote future the unexpected.
More and more each day, we’re experiencing the rapid development and application of big data and artificial intelligence (AI) systems. To what extent are these systems already being shaped by quantum science and technology, and what do you consider to be the risks and opportunities of quantum physics in AI (and vice versa)?
The ongoing global, rapid and revolutionary developments in big data applications, AI and machine learning, have particularly been triggered through advances in high-performance computing during the last decade. The processors and their fabrication are based on highly advanced quantum technology, involving semiconductor materials and extreme ultraviolet (XUV) lasers. Hence, the boom in AI would simply be impossible without quantum mechanics.
The foundations of AI were laid in physics, and big data was a topic in particle physics, for example, long before it gained the general significance it has today. Nowadays, vice versa, machine learning methods are increasingly being used in physical research and development, and hence, of course, also for devising new quantum technologies.
We are observing more and more how methods in AI, quantum physics and quantum computing are becoming increasingly intertwined. For example, there are the research areas of physics-inspired machine learning and also quantum machine learning, the integration of quantum algorithms within machine learning programmes. The interlocking of these two rapidly developing methods – quantum algorithms and AI – certainly offers undreamt of synergy effects. However, the speed at which this is happening also harbours potential risks.
As President of the German Physical Society (DPG), a founding partner of IYQ, how do you see the legacy of the last 100 years of quantum science informing your work in support of the objectives of the International Year?
One hundred years ago, Göttingen, Germany, played a central role in creating quantum physics as we know it today. In 1925, the fundamental laws of quantum mechanics were formulated there for the first time. Hence, in view of what happened in Göttingen, IYQ is of particular relevance for the physics community in Germany. Within DPG we have thus dedicated the whole year 2025 to quantum physics! We are celebrating its successes but, in particular, will set our sights on the future prospects of quantum mechanics.
To this end, DPG is offering a comprehensive outreach programme over the year, comprising five thematic lines: (i) quantum physics in research and quantum technologies; (ii) quanta at school, playing with quanta: modern quantum technologies can provide new impetus for teaching in order to increase public awareness and broad education in the natural sciences as a whole; (iii) quanta in music, in philosophy, art, movies and literature; (iv) quanta in the professional world, career and reaching out to society; and (v) the path to the modern quantum world and beyond.
Quantum theory is one of mankind's greatest fundamental insights into the world we live in. We can be enthusiastic but should not promise too much for a foreseeable future. DPG emphasizes the immense importance of quantum science and advocates the effective promotion of strong and free research into the fundamentals of quantum physics. At the same time, and as part of the legacy of the last 100 years, science is called upon to accompany new developments in quantum technologies responsibly and for the benefit of mankind, and to carefully consider possible societal impacts. This also includes being transparent and informing society about opportunities but also potential risks. Historically, and accentuated by the current global situation, the strategic security potential of quantum technologies is also obvious.
You have pointed out that physics has a key role to play in the necessary transformation towards a secure, fossil-free energy supply. What are your hopes and expectations as far as the potential for quantum science and technology to help solve the climate crisis?
As far as the major global challenges of our time are concerned, rapid climate change is certainly at the top of the list. To mitigate climate change physics is playing and will play a key role in the necessary transformation of the energy supply towards defossilization. Here, photovoltaics is a prime example of applied quantum physics and has the potential to tackle the climate crisis quickly, because the problem is urgent. As predicted by the International Energy Agency, the growth rate of photovoltaics over the next decade is far ahead of all other sources for electrical energy supply. And photovoltaics are not just relying on Einstein’s photo effect discovered more than 100 years ago: today’s high-tech solar panels involve way more facets of quantum and semiconductor technology. However, further research and development in energy storage systems and (smart) electrical grids is also necessary for a rapid and large-scale transformation towards renewables and a sustainable energy management.
Furthermore, while it is important that the technologies mentioned are further developed at full speed, the long-term perspective must also be kept in mind.
This includes quantum physics-based technologies for quasi-fossil-free energy generation such as nuclear fusion. As the time horizon for large-scale commercial electricity production is currently still estimated at several decades, nuclear fusion technologies are not yet available to deal with the urgent need to limit global warming. However, fusion research and development should continue to be promoted and supported as a long-term option.
IYQ events are taking place all over the world, facilitating scientific dialogue across borders and cultures and inspiring young people to contribute to another quantum century. What is your view on the value of multilateralism for ensuring continued global knowledge of and investment in quantum and other kinds of science?
I am firmly convinced that in a world that is globally characterized by tendencies towards fragmentation within and between societies, multilateral networking by the international scientific community is more important than ever.
On the one hand, quantum science, with its fascinating possibilities and its globally perceptible momentum, currently offers perfect conditions for stronger global networking. Here, the diverse events initiated and orchestrated by IYQ certainly have an identity-building effect.
During IYQ, DPG is organizing a series of outstanding events aimed at international exchange in quantum science. For example, Ghana was the guest country with a highlighted symposium at our DPG Annual March Meeting. Furthermore, this autumn we are organizing an additional large, international conference in Göttingen, the birthplace of quantum mechanics, which features facets of quantum physics in all its breadth. And by the way, at the end of June my colleague, Thomas Konrad (University of KwaZulu-Natal, Durban, South Africa), supported by several colleagues from the sphere of DPG, is organizing a conference entitled ”Quantum Science and Technology across Africa”, aiming at the development of a pan-African quantum network.
On the other hand, the rapid development of quantum technologies also harbours the risk of new global dependencies. When we talk about digital sovereignty, this should certainly also apply to quantum technologies.
What is it like to be a condensed matter physicist? How does your line of work impact how you see and move through the world, and what are you working on or planning in terms of research?
Between the two physical extremes, the microcosm of elementary particles and the macrocosm of astrophysics, lies a fascinating and multi-layered world: the world of condensed matter. At first glance, matter seems familiar to us because it is visible all around us. But to understand why matter and materials are the way they are, and in particular how new, fascinating material properties can be tailored in the twenty-first century and enable new technologies, quantum physics again plays a crucial role.
In our research, we deal on the one hand with ultra-thin materials composed of a few atomic layers, which can be imagined as being stacked together like Lego bricks. The electric current in these quantum materials is dominated by quantum effects, and we calculate how these can be cleverly exploited in future electronic components. In addition, we are studying quantum control i.e. how to stabilize, switch and control quantum mechanical objects, also with regard to operations in future quantum computing devices.
Hence, for me as a condensed matter physicist, quantum physics is our daily bread and butter: in my lectures and in research, in daily discussions with my colleagues and group members. In a sense, we quantum physicists operate in a hybrid sphere: the quantum world with its counter-intuitive phenomena and the ordinary, classical world of our environment.
The UN Chronicle wishes to thank Professor Dr. Richter for sharing his expert insights into quantum science and its growing global importance.
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