Surprising and unexpected in a quantum system

Surprising and unexpected in a quantum system

Physicists at ETH Zurich have observed a surprising twist in a quantum system caused by the interplay between energy dissipation and coherent quantum dynamics. To explain it, they found a concrete analogy to mechanics.

“No scientist thinks in formulae”, Albert Einstein allegedly once told his colleague Leopold Infeld. In fact, especially for physicists, who deal with such abstract things as quantum physics, it is often immensely useful to work with concrete images rather than mathematical symbols. A team of researchers led by Tilman Esslinger, professor at the Institute for Quantum Electronics at ETH Zurich, experienced this when they recently discovered a new effect in their quantum mechanical system. Although they were studying tiny atoms and light particles in their experiment, they were able to understand their observations better through a catchy image: a shaft turning inside a bearing. Their results have recently been published in the journal Science.

A complex quantum system

“We hadn’t really been looking for that effect at all”, says Esslinger. “Only with hindsight did we understand what our data mean.” He and his co-​workers had tackled a very complex topic: a quantum system in which the individual particles interact strongly with one another and that is simultaneously driven from the outside and also dissipative. “Dissipative” means that the quantum states of the particles do not just evolve coherently in time – that is, such that their superposition states remain intact.

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Source: “Unexpected twist in a quantum system”, Oliver Morsch, ETH Zurich News