Calculations from TU Wien (Vienna) have revealed that time crystals can be created in a fundamentally different method than previously assumed. The results were reported in Physical Review Letters.
Correlations between quantum particles result in a rhythmic signal, without the need for an external beat to set the tempo. Image Credit: TU Wien
There are numerous rhythms in nature: the Earth’s rotation around the sun determines the seasons, and a pendulum clock’s oscillation causes it to tick. Fundamental equations can be used to explain these events.
Regular rhythms, on the other hand, might emerge in a completely different way: spontaneously, without an external clock, through the complicated interaction of numerous particles. Instead of uniform disorder, a set rhythm forms, often known as a “time crystal.”
Quantum physical connections between particles, which were previously considered to be detrimental to the formation of such phenomena, can now stabilize time crystals. This is a fascinating new perspective on the quantum mechanics of many-particle systems.
Space Crystals and Time Crystals
When a liquid freezes, the particles lose their spatial order. In the liquid, they move wildly and randomly, with no structure. When the liquid freezes, it creates a crystal in which the individual particles are arranged in a highly particular and regular pattern.
A liquid seems to be the same everywhere, has the same qualities, and is entirely symmetrical in all directions. However, in a crystal, this symmetry is broken: there is now a regular structure, as well as a direction that varies from the others.
Can this type of symmetry breaking occur over time? Is it feasible for a quantum system to be initially disordered in time, with every point in time being identical to the next, but for that temporal order eventually to emerge?
Quantum Fluctuations: Harmful or Useful?
This question has been the subject of intensive research in quantum physics for over ten years.
Felix Russo, Postdoctoral Researcher, TU Wien
In fact, it has been demonstrated that so-called time crystals can exist, where a temporal rhythm emerges spontaneously without any external force setting the pace.
Russo added, “However, it was thought that this was only possible in very specific systems, such as quantum gases, whose physics can be well described by mean values without having to take into account the random fluctuations that are inevitable in quantum physics. We have now shown that it is precisely the quantum physical correlations between the particles, which were previously thought to prevent the formation of time crystals, that can lead to the emergence of time-crystalline phases.”
Similar to how the smoke from an extinguished candle can occasionally form a regular series of smoke rings (a phenomenon whose rhythm is not dictated from outside and which cannot be understood from single smoke particles) the intricate quantum interactions between the particles cause collective behavior that cannot be explained at the level of individual particles.
Particles in the Laser Lattice
“We are investigating a two-dimensional lattice of particles held in place by laser beams. And here we can show that the state of the lattice begins to oscillate – due to the quantum interaction between the particles,” Russo stated.
The study provides a chance to better comprehend the theory of quantum many-body systems, opening the path for new quantum technologies and high-precision quantum measurement techniques.
Journal Reference:
Russo, F. and Pohl, T. (2025) Quantum Dissipative Continuous Time Crystals. Physical Review Letters. doi.org/10.1103/dc2s-94gv