Quantum physics still holds major puzzles and surprises. In particular, when it comes to quantum systems in which many particles interact with each other, important questions remain unanswered. A new Special Research Programme (SFB), funded by the Austrian Science Fund FWF, aims to provide answers in the coming years: Prof. Thomas Pohl from the Institute of Theoretical Physics at TU Wien will lead the project “Qnnect,” which will investigate how neutral atoms and molecules can be manipulated to display key quantum-physical effects—effects that also occur in other quantum systems that are much more difficult to control.
The Principal Investigators include Tim Langen (Atominstitut, TU Wien) as well as researchers from the Austrian Academy of Sciences, the University of Innsbruck, ISTA (Klosterneuburg), and the University of Vienna. The project is funded with over four million euros and is initially planned for a duration of four years.
One particle is complicated — many particles are unbelievably complicated
When Erwin Schrödinger wrote down his “Schrödinger equation” almost exactly one hundred years ago—the foundational equation of modern quantum research—he was initially describing the simplest quantum system that exists: a single hydrogen atom with one electron orbiting a nucleus. Even then, it was clear: more complex objects composed of several particles are vastly more difficult to describe.
To this day, many-body quantum physics remains an extremely challenging field. If one wants to analyze larger atoms or molecules quantum mechanically—or even calculate the properties of new materials—the equations of quantum physics quickly become so complex that even the world’s most powerful computer clusters are hopelessly overwhelmed.
Simulating quantum systems — with quantum systems
Sometimes, however, you don’t actually need to solve the equations of quantum physics to understand a quantum system. If a system is too complex to simulate on a computer, there is another possibility: you can simulate it using a different quantum system.
This idea traces back to Physics Nobel laureate Richard Feynman: one can design tailor-made quantum systems whose parameters can be adjusted at will. By observing how these systems evolve, one can learn something about other quantum systems that cannot be adjusted so easily. In essence, an experimentally inaccessible system is mapped onto another system that is much easier to handle.
Analog experiments exist in other areas of physics as well: you can study water waves to learn something about sound waves, or analyze airflow around architectural models in a wind tunnel to predict how the wind will affect the finished building. In quantum physics, such analog experiments—known as “quantum simulators”—make it possible to answer questions that are practically inaccessible by any other means.
Neutral atoms as building blocks for new systems
The new research project aims to enable the use of large numbers of neutral atoms and molecules as quantum simulators. They can be manipulated with laser beams, and for quantum standards they can interact with each other over relatively large distances. They can be quantum-entangled with one another. In this way, one can deliberately construct a many-body system tailored to answer a very specific question.
Achieving this requires a deep theoretical understanding of such systems—which is why the new Special Research Programme brings experimental and theoretical research groups together in close collaboration.
Contact:
Prof. Thomas Pohl
Institute for Theoretical Physics
TU Wien
+43 1 58801 13670
thomas.e136.pohl@tuwien.ac.at