Quantum physicist Aspelmeyer receives Austria's most highly endowed science prize

The 52-year-old Aspelmeyer, born on 14 June 1974 in Schongau in Upper Bavaria, is one of the world's most renowned researchers in the field of quantum optics and quantum optomechanics. After studying physics and philosophy, he received his doctorate in physics in 2002 from the Ludwig Maximilian University of Munich.

Path from solid-state physics to quantum physics

His interest in the history of science brought him to a working group at the Max Planck Institute for the History of Science that dealt with the topic of quantum gravity. "This was also the reason why, after his doctorate in 2002, he switched from the field of solid-state physics to quantum physics - and joined the team of quantum physicist Anton Zeilinger at the University of Vienna as a Humboldt Foundation fellow."

Aspelmeyer recalls his beginnings with Zeilinger: "I had the insane luck that Zeilinger was bold enough to bring a doctorate from a different field into the team." This experience still shapes his dealings with young scientists today: He hopes that he himself has both the courage and the luck to bring extraordinary young researchers into his team.

Aspelmeyer stayed in Vienna, also joined the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW) after its founding in 2004, and in 2009 chose a professorship at the University of Vienna over offers from Oxford and Calgary: "It was the best offer, the best framework conditions." Ten years later, he succeeded Anton Zeilinger as scientific director of IQOQI Vienna.

Freedom and flexibility for research

The award is endowed with two million euros and earmarked for research. It supports the laureate's research and guarantees freedom and flexibility in its execution. "This year's FWF Wittgenstein Prize not only honors Markus Aspelmeyer's outstanding scientific career, but is also an investment in one of the most ambitious endeavors in modern physics, one that enriches Austria's successful tradition in quantum research with another promising chapter," according to the international FWF jury.

Aspelmeyer's research revolves around one of the great open questions in physics: Can quantum effects and gravity be brought together in a single experiment? "In my research group, we have invested a lot of time over the last 20 years in driving solid-state objects like small trampolines into the quantum regime." These objects are a hundred times smaller than a grain of sand, but still consist of several hundred million atoms and are held in levitation by a strongly focused laser beam in a high vacuum while simultaneously being cooled by the laser light. And indeed cooled to the point where their kinetic energy approaches absolute zero (minus 273 degrees Celsius).

Small trampolines in the quantum regime

What remain are motions ("quantum fluctuations") that no longer follow the laws of classical physics, but rather those of quantum physics. The goal: "A gravity experiment that can no longer be described solely by Einstein's general theory of relativity," says Aspelmeyer.

In 2021, he and his team finally succeeded in measuring the smallest gravitational force ever determined: the attractive force of a gold bead weighing 90 milligrams. That is roughly as heavy as a ladybug and attracts other objects with an acceleration that is 30 billion times smaller than Earth's gravitational pull. "I took out my notebook and started calculating and suddenly realized: Wow, that just might work," the physicist recalled of the moment when he estimated the orders of magnitude.

The path to quantum gravity

During a seminar in 2012, he had the idea of whether the small vibrating trampolines he worked with might have enough mass to also move in the direction of gravity experiments. The challenges in the direction of gravitational measurements are great: The physicist recalls a visitor from Canada who, upon hearing of the plans, remarked: "Markus, that's enough now. You can't even measure the gravitational field of that chair over there." But Aspelmeyer was not deterred.

In the late 1950s, the prevailing view was that gravitational waves and the gravitation of quantum objects were interesting effects, but ones so small that it was impossible to demonstrate them in an experiment. "For gravitational waves, we have known since 2015 that this is not true: We can measure gravitational waves, by now almost daily." What seemed just as inconceivable decades ago is what is possible in the laboratory today: "Sixty or seventy years ago, it was unthinkable that the experimental capabilities would ever develop to this point."

The road to the observation of quantum gravity is still a long one: While the size of objects at which quantum effects are observed still needs to be increased a hundredfold, the gravitational force of objects that are a factor of 100 smaller than at present must be successfully measured. "As an experimental physicist, you always give yourself a buffer, like three years, and that's why the experiment will be finished in 17 years," says Aspelmeyer. He adds: "The timeline is 17 years, and that has to do with the European research system, because we have the system of mandatory retirement." Asked when he personally expects the breakthrough, he answers: "For me, it will be in 20 years."

International awards and funding

Aspelmeyer has received numerous international awards, most recently the 2025 Prize for Fundamental Aspects from the European Physical Society for his groundbreaking contributions to quantum optomechanics. After already receiving a "Starting Grant" in 2009 and a "Consolidator Grant" in 2015 from the European Research Council ERC, in 2020 he received an ERC "Synergy Grant" worth 13 million euros together with colleagues from Innsbruck and Zurich to push the quantum physical principle of delocalization to its outermost limit: They want to position a solid-state body consisting of billions of atoms at two locations simultaneously. But this is far from the end of the road: With the Wittgenstein Prize, he hopes to take a step further in this "great, long-term undertaking."

The father of two sits on the board of the FWF Excellence Cluster "Quantum Science Austria" and is a member of the American Physical Society, the ÖAW, and the Academy of Sciences and Arts in Hamburg. Aspelmeyer shares not only a passion for sailing with Zeilinger, although, unlike in the past, when he sailed the demanding 470-class regatta, he currently has to put this passion aside for work-related reasons. He also moderated the legendary ad-hoc event in the packed Ludwig Boltzmann lecture hall of the University of Vienna's Faculty of Physics just a few hours after the announcement of the 2022 Physics Nobel Prize, at which Anton Zeilinger was celebrated.

Wittgenstein and the limits of language

"The fact that our prosperity is closely tied to strong basic research is an insight that is almost 100 years old," Aspelmeyer emphasizes. "And Austria has delivered incredibly well on this over the last more than 30 years." The prize's namesake also comes up in his reflections: "The limits of my language are the limits of my world" is a quote from Wittgenstein that expresses precisely what quantum physics holds up to us as a mirror: We are in a situation in which we can no longer describe nature by means of our language. Another example from the Tractatus is: "The world is everything that is the case." If he were to view quantum physics the way we see it today, the Tractatus would begin differently, namely with: "The world is everything that could possibly be the case."

Regarding his motivation, Aspelmeyer says: "It has always been the case for me that when things interested me, I started to engage with them." An outstanding teacher and a concentrated dose of popular science books such as "One Formula Changes the World" by Harald Fritzsch or "A Brief History of Time" by Stephen Hawking, which came out in his youth, played a large role in his decision to study physics at the University of Munich. "My favorite example is of course the experiments of my colleague Markus Arndt (Wittgenstein Prize laureate 2008) with his molecular interference experiments." When asked about the reaction of those around him to the prize, he says with a smile: "My 15-year-old son just said: I didn't even know you were such a good researcher."

With the Wittgenstein Prize, Aspelmeyer receives not only personal recognition, but also the means to consistently pursue his long-term project. The jury sees the awarding of the prize as "an investment in one of the most ambitious endeavors in modern physics, one that enriches Austria's successful tradition in quantum research with another promising chapter."