Researchers discover quantum time crystal and define a new phase of matter

A time crystal is a system that is in constant motion and follows its own beat. Surprisingly, physicists at TU Wien have now shown that quantum fluctuations – usually considered a disruptive factor – can enable these stable oscillations. Their results provide insights into previously unknown behavior of matter in time and space.

Nature and Technology

by Phila Reymbold/red

March 2, 2026

Time crystals are an unusual phenomenon in modern physics: systems that do not come to rest but perpetually maintain a rhythm of their own. The idea was born by Nobel Prize laureate Frank Wilczek, who in 2012 predicted the existence of time crystals in the ground state of a quantum system. This type of time crystals was soon disproved as a concept, but researchers investigated other physical scenarios in order to observe crystallization in time. Surprisingly, the breakthrough was achieved in so-called open quantum systems, for instance for atoms that continuously dispense energy to their surroundings. Until recently, quantum physics was considered a necessary evil in this context, as it describes the tiny systems in which time crystals exist, however quantum fluctuations were until recently believed to prevent the crystal formation. The research group of physicist Thomas Pohl at TU Wien has now been able to demonstrate that there are also time crystals whose stability only develops because of genuine quantum effects. Not only deepening our understanding of the behavior of matter and its physical properties, this discovery also opens up new perspectives for quantum technologies.

Permanent timekeepers

Physicists at TU Wien have been able to demonstrate that there are also time crystals whose stability only develops because of genuine quantum effects. This discovery opens up new perspectives for quantum technologies.

Space and time

Time crystals differ from ordinary crystals in that their order does not arise in space but in time. Whereas the stability of a classical crystal results from a periodic spatial structure, a time crystal exhibits a regular temporal repetition. When an ice crystal forms, for instance, an alignment develops where none existed before: in liquid water, molecules float around turbulently before aligning themselves to form structured ice. It is this broken symmetry that also defines time crystals. A system that was originally temporally disordered evolves into a periodic– i.e. regularly repeating –state and finds its own rhythm.

Time crystals as permanent timekeepers

This said, not every periodic movement is a time crystal. In many systems, such as in a pendulum, an oscillation is determined by external excitation or by the geometry of the system, and it disappears as soon as there is friction. Real time crystals, on the other hand, are extremely stable despite energy losses. Their frequency does not correspond to a simple resonance, but emerges through a complex interaction of many particles. In this sense, time crystals are a phase of matter, comparable to “liquid” and “solid,” only in time. A time crystal could therefore serve as a permanent clock for the smallest applications, conceivably even for quantum technologies or as a reference oscillation for precise frequency measurements. But how do you create them?

The mean-field model

Recently, time crystals have been observed in very different systems: from optomechanical resonators to oscillations in liquid crystals that can be seen with the naked eye. They all have one aspect in common: they consist of microscopically small building blocks, and of so many of these building blocks that they can be described well using statistics: they can be modeled using semi-classical models, known as “mean-field” models, which ignore many-body quantum fluctuations. Until recently, it even seemed as if the fluctuations of quantum physics generally undermined the stability of time crystals. Researchers in Vienna have now been able to refute this. But before we get to their findings, we need to understand what a semi-classical mean-field model is.

Imagine a group of individuals who exchange opinions among each other. Each individual has their own opinion, but this opinion continuously changes under the influence of the opinions of those around them. In order to be able to describe this system exactly, every exchange of opinions needs to be modeled – which can be a very time-consuming endeavor in case of large crowds. The mean-field approach is a very simple method of approximation, as it only describes the average, or mean, opinion. Hence, one simulates only a single person who is influenced by the mean opinion of the others until a consensus is reached. The name mean-field is derived from the fact that one describes interaction with the mean field of opinions. In this example, the exchange of opinions between two individuals is neglected; in the physics analogy this corresponds to neglecting the two-particle quantum correlations.

Graphical representation of atoms on a lattice, light waves, and a stopwatch — Many neatly arranged atoms can together develop a behavior in which the system no longer looks the same at all times, but follows its own “internal” clock. © TU Wien

First quantum time crystals discovered

At TU Wien, theoretical physicists Thomas Pohl and Felix Russo, supported by funding from the Austrian Science Fund FWF, wondered what would happen if the exchange of opinions were also simulated – not for a crowd of people but in a real quantum system. Would it still be possible to create time crystals, or would they be disrupted by the quantum fluctuations? Pohl and Russo modeled an arrangement of atoms in a lattice of laser light. In this way, they discovered a type of time crystal that can only be described using a full-fledged quantum model.

“Until now, time-crystal oscillations were attenuated in systems where a mean-field approximation is not permitted. This led to the assumption that quantum fluctuations were unfavorable for a stable time order,” explains Felix Russo. “Our computations now show that quantum fluctuations do not necessarily have a damping effect. On the contrary, they can even generate time crystal oscillations!”

Search for related systems

In its current form, the new quantum time crystal is still difficult to implement in experiments. The research group is therefore looking for related systems in which similar effects could be observed under more accessible laboratory conditions. This search for a suitable system is all the more exciting now that we know that quantum interactions themselves can produce the perpetual clock that makes time crystals so unique.

This could lead to the development of extremely accurate quantum clocks that are very well aligned technologically to quantum processors and could thus increase the performance of future quantum computers.

About the researchers

Thomas Pohl heads a research group at the Institute of Theoretical Physics at TU Wien. Felix Russo is a doctoral student there. The researchers' work focuses on the description of open quantum systems in non-equilibrium. The new findings were obtained in the context of the “Quantum Science Austria“ Cluster of Excellence, which is a national initiative to support quantum sciences that is funded by the Austrian Science Fund FWF with 21 million euros.