Scientists at the University of Innsbruck have discovered that a strongly interacting quantum gas can stop absorbing energy when repeatedly driven by laser pulses, entering a stable state called many-body dynamical localization. This challenges classical expectations of inevitable heating in driven systems. The finding highlights the role of quantum coherence in maintaining order amid constant forcing.
Researchers in Hanns Christoph Nägerl's group at the University of Innsbruck's Department of Experimental Physics conducted an experiment using a one-dimensional quantum fluid composed of strongly interacting atoms cooled to just a few nanokelvin above absolute zero. They applied laser light to create a lattice potential that switched on and off rapidly, effectively kicking the atoms repeatedly.
Initially, the atoms absorbed energy as expected, but after a short period, their momentum distribution froze, and kinetic energy absorption ceased. The system reached a state of many-body dynamical localization (MBDL), where quantum coherence and many-body entanglement prevented thermalization and diffusive behavior despite ongoing interactions and driving.
"In this state, quantum coherence and many-body entanglement prevent the system from thermalizing and from showing diffusive behavior, even under sustained external driving," Nägerl explained. "The momentum distribution essentially freezes and retains whatever structure it has."
Lead author Yanliang Guo noted the unexpected orderliness: "We had initially expected that the atoms would start flying all around. Instead, they behaved in an amazingly orderly manner."
Theory collaborator Lei Ying from Zhejiang University emphasized the counterintuitive result: "This is not to our naïve expectation. What's striking is the fact that in a strongly driven and strongly interacting system, many-body coherence can evidently halt energy absorption. This goes against our classical intuition and reveals a remarkable stability rooted in quantum mechanics."
To test robustness, the team introduced randomness to the driving sequence, which quickly disrupted the localization. Momentum spread resumed, and energy absorption increased without bound, underscoring quantum coherence's essential role.
This discovery, published in Science (2025; 389 (6761): 716), has potential implications for quantum technologies. Preventing heating remains a key challenge for quantum simulators and computers, which depend on preserving delicate states against decoherence. "This experiment provides a precise and highly tunable way for exploring how quantum systems can resist the pull of chaos," Guo said. The work was supported by the Austrian Science Fund FWF, the Austrian Research Promotion Agency FFG, and the European Union.