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American, Austrian and Brazilian physicists have shown that shaking ultra-cold Bose-Einstein condensates (BECs) can cause them to divide into uniform segments or break into unpredictable bursts, depending on the frequency of shaking. .
"It is remarkable that the same quantum system can give rise to such different phenomena," said Rice University physicist Randy Hulet, co-author of a study on the work published online today. In the journal Physical examination X. Hulet's lab conducted the experiments of the study using lithium BECs, tiny clouds of ultra-cold atoms parading as though they formed a single entity, or a wave of matter. "The relationship between these states can teach us a lot about multi-body complex quantum phenomena."
The research was conducted in collaboration with physicists from the University of Technology Vienna (Austria) and the University of São Paulo in Brazil, São Carlos.
The experiments evoke the discovery by Michael Faraday in 1831, that undulating patterns were created on the surface of a fluid in a bucket agitated vertically at certain critical frequencies. The patterns, called Faraday waves, are similar to the resonance modes created on drum skins and vibrating plates.
To study Faraday waves, the team confined the BECs to a one-dimensional linear waveguide, which resulted in a cigar-shaped BEC. The researchers then shook the BECs using a slow-oscillation weak magnetic field to modulate the strength of the interactions between the atoms in the 1D waveguide. The Faraday scheme appeared when the modulation frequency was set near a collective mode resonance.
But the team also noticed something unexpected: when the modulation was strong and the frequency was much lower than the Faraday resonance, the BEC was broken into "grains" of varying size . Research scientist Rice, Jason Nguyen, co-lead author of the study, discovered that grain size was widely distributed and persisted even longer than modulation time.
"Granulation is usually a random process observed in solids such as glass breakage or the spraying of a granular stone of different sizes," said Axel Lode, co-author of the study, which works together with TU Wien and Wolfgang Pauli. Institute of the University of Vienna.
The images of the quantum state of the BEC were identical in each Faraday wave experiment. But in the granulation experiments, the images looked completely different each time, even though the experiments were performed under identical conditions.
According to Lode, the variation in granulation experiments is the result of quantum correlations – complex relationships between quantum particles difficult to describe mathematically.
"A theoretical description of the observations proved difficult, as standard approaches could not replicate observations, particularly the wide distribution of grain sizes," Lode said. His team helped interpret the experimental results using a sophisticated theoretical method and its implementation in software, which accounted for quantum fluctuations and correlations that typical theories do not deal with.
Hulet, professor of physics and astronomy Fayez Sarofim of Rice and a member of the Rice Center for Quantum Materials (RCQM), said the findings had important implications for research on turbulence in quantum fluids, a problem not resolved in physics.
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Material provided by Rice University. Note: Content can be changed for style and length.
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