100 Years Of Quantum Physics: Science Of Inconceivable

13 January 2025

Quantum physics has changed our lives decisively in recent decades. One hundred years after the mathematical formulation of quantum mechanics, the United Nations has declared 2025 to be the International Year of Quantum Science and Technology. Quantum physicist Prof. Dr. Tommaso Calarco from Forschungszentrum Jülich will attend the launch event in Germany and discuss the topic of quantum physics with representatives from science, industry, and politics. In this interview, he talks about the developments over the past one hundred years as well as quantum technology research at Jülich and provides an outlook on the progress that can be expected in the coming years.

Prof. Calarco, many people wonder what quantum physics or quantum mechanics actually is. How would you explain quantum physics to your grandparents? How does it differ from classical physics?

Quantum mechanics deals with the smallest particles - atoms, electrons, or photons - and describes their behaviour mathematically. It differs to classical physics in that an atom can be in two different places at the same time, for example. We humans cannot imagine this, not because we are not clever enough, but because it is fundamentally impossible to intuitively conceive what's happening at this microscopic level. The laws of quantum mechanics and the impossibility of obtaining a classical picture of them provided the basis for the Nobel Prize in 2022. The three laureates verified the rules of quantum physics again and again in experiments and cleared the way for a new quantum technology era. You could say that the difference between classical physics and quantum physics is also philosophical, but it is important for technological applications.

How has quantum physics influenced our everyday lives over the last 100 years?

Electronics means that electrons are used in tiny devices, for example to calculate, make phone calls, or listen to music. All information technology is based on electronics or photonics - where quantum coherent light is used to transmit information on a global scale. Both developments would be inconceivable if we were not able to understand and influence the behaviour of the smallest particles. Examples of applications include transistors, computer processors, and lasers, which are used not only in information transmission but also in medicine and diagnostics. Magnetic resonance imaging (MRI), for example, requires the quantum mechanical description of the properties of microscopic particles in order to image structures in the human body. Quantum mechanics is present everywhere in our lives.

Scientists at Jülich are researching new quantum technologies. What's unique about this research at Jülich?

We have just talked about first-generation quantum technologies. Jülich colleagues also worked successfully in this field - for example, Nobel laureate Prof. Dr. Peter Grünberg. His research led to new applications in computer hard drives. Today, Jülich is working on second-generation quantum technologies. While in conventional electronic circuits, a large number of electrons flow in the form of electric current, in the new quantum technologies individual atoms, individual electrons, or individual photons are manipulated individually.

What makes work at Jülich unique is that we cover the entire value chain. The Helmholtz Nanofacility manufactures the smallest quantum chips, which are combined with common electronics and integrated into quantum systems. The appropriate software and firmware for these systems are also programmed in Jülich. We have already integrated the first quantum computer prototypes into the high-performance computing environment of the Jülich Supercomputing Centre. This enables us to use prototypes for initial specific applications and make them available to stakeholders in science and industry. That is a unique selling point. In other words, we cover not only the entire production chain from hardware to software, but also apply the quantum computing systems and make them available to a user community via JUNIQ, the Jülich UNified Infrastructure for Quantum computing. JUNIQ is unique and provides inspiration for other infrastructures in Europe.

What influence could quantum physics have on technological developments over the next 100 years?

Niels Bohr once said: "Prediction is very difficult, especially about the future." We scientists should be careful about predicting what will happen in the next 100 years. Thomas Watson, the former CEO of IBM, reputably said in 1943 that the world would need 'maybe five computers'. Nowadays we can laugh about this, but it also shows how developments can surprise us. What we can expect is an acceleration of computing processes, and this includes AI applications. But that will take another 20 years at least. We also anticipate that by transmitting individual photons, we'll be able to establish secure communication. In sensor technology, the measurements of many phenomena could become much more precise, enabling the real-time measurement of individual neuron activity, for instance. This would open up new possibilities in diagnostics. Time measurement could also become more precise and enable satellite navigation from the current metre range to the centimetre or millimetre range - an important aspect for autonomous driving. However, I expect that most of the applications are not yet known. Although much progress has been made, there are still major challenges ahead before we can actually use such technologies in the future.

Prof. Dr. Tommaso Calarco

Director, Institute for Quantum Control PGI-8

• Peter Grünberg Institute (PGI)
• Quantum Control (PGI-8)