Quantum systems and bee flight

At first glance, a system consisting of 51 ions may seem easily manageable. But even if these charged atoms are only changed between two states, the result is greater than two quadrillion (1015) different commands that the system can support.

The behavior of such a system is almost impossible to calculate with conventional computers, especially since an excitation introduced into the system can propagate erratically. Excitation follows a statistical pattern called Lévy’s flight.

A feature of such movements is that in addition to the expected smaller jumps, significantly larger jumps also take place. This phenomenon is also seen in thefts of bees and in unusual ferocious movements in the stock market.

Simulating quantum dynamics: traditionally a difficult task

While simulating the dynamics of a complex quantum system is a very difficult task even for traditional supercomputers, the task is child’s play for quantum simulators. But how can the results of a quantum simulator be verified without the ability to perform the same calculations as them?

Observation of quantum systems has indicated that it might be possible to represent at least the long-term behavior of such systems with equations like those the Bernoulli brothers developed in the 18th century to describe the behavior of fluids.

To test this hypothesis, the authors used a quantum system that simulates the dynamics of quantum magnets. They were able to use it to prove that after an initial phase dominated by the effects of quantum mechanics, the system could indeed be described with equations of the familiar fluid dynamics type.

Moreover, they showed that the same Lévy Flight statistics that describe the search strategies used by bees also apply to fluid dynamics processes in quantum systems.

Captured ions as a platform for controlled quantum simulations

The quantum simulator was built at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences on the campus of the University of Innsbruck. “Our system effectively simulates a quantum magnet by representing the north and south poles of a molecular magnet using two energy levels of the ions,” explains Manoj Joshi, scientist at IQOQI Innsbruck.

“Our greatest technical advance was the fact of having succeeded in addressing each of the 51 ions individually”, observes Manoj Joshi. “As a result, we were able to study the dynamics of any desired number of initial states, which was necessary to illustrate the emergence of fluid dynamics.”

“While the number of qubits and the stability of quantum states are currently very limited, there are questions for which we can already use the enormous computing power of quantum simulators today,” says dynamics professor Michael Knap collective quantum at the Technical University. from Munich.

“In the near future, quantum simulators and quantum computers will be ideal platforms for studying the dynamics of complex quantum systems,” explains Michael Knap. “Now we know that after a while these systems follow the laws of classical fluid dynamics. Any significant deviation from this indicates that the simulator is not working properly. »


Observation of emergent hydrodynamics in a long-range quantum magnet. MK Joshi, F. Kranzl, A. Schuckert, I. Lovas, C. Maier, R. Blatt, M. Knap, CF Roos. Science, 13.05.2022 – DOI: 10.1126/science.abk2400 [https://arxiv.org/abs/2107.00033]

More information:

The research activities were funded by the European Community under the Horizon 2020 research and innovation program and the European Research Council (ERC); by the German Research Foundation (DFG) as part of the Munich Center for Quantum Science and Technology (MCQST) cluster of excellence; and by the Technical University of Munich through the Institute for Advanced Study, which is supported by funding from the German Excellence Initiative and the European Union. Additional support was provided by the Max Planck Society (MPG) under the auspices of the International Max Planck Research School for Quantum Science and Technology (IMPRS-QST); by the Austrian Science Fund (FWF) and the Federation of Austrian Industries in Tyrol.

The authors Prof. Michael Knap (TU Munich) and Prof. Rainer Blatt (University of Innsbruck) are active in the “Munich Quantum Valley”, an initiative to establish a center for quantum computing and quantum technology (ZQQ ) over the next five years. years. Here, three quantum computers are to be built from superconducting qubits as well as ion and atom qubits. Members of the Munich Quantum Valley eV association include the Bavarian Academy of Sciences and Humanities (BAdW), Fraunhofer (FhG), German Aerospace Center (DLR), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Ludwig-Maximilians-Universität Munich (LMU), Max Planck Society (MPG) and Technical University of Munich (TUM).

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