Physicists determine when time can flow both faster and slower at the same time

Scientists have proposed an experiment that could, for the first time, test one of the most unusual ideas at the intersection of quantum mechanics and relativity — the possibility that time itself can exist in a state of superposition.

The study was published in the journal Physical Review Letters. The authors, led by Igor Pikovsky, believe that modern quantum technologies are already approaching the level of precision needed to observe truly exotic effects in the flow of time.

Time in Einstein’s physics and quantum uncertainty

According to Albert Einstein’s general theory of relativity, the passage of time depends on velocity and gravitational fields: the stronger the gravity or the higher the speed, the slower time passes.

However, when attempts are made to combine relativity with quantum mechanics, the picture becomes even stranger. In the quantum world, objects can exist in a superposition — multiple states at once. A classic example is Schrödinger’s cat, which is considered both alive and dead until it is observed. Researchers suggest that something similar could apply to time itself.

Ion clocks as a testing tool

To test this hypothesis, scientists propose using the world’s most precise ion clocks. In these devices, individual ions are cooled to near absolute zero and their quantum states are carefully controlled using lasers.

Modern ion clocks are already capable of detecting time dilation caused by thermal atomic motion at an extremely subtle level.

The research was conducted in collaboration with scientists from the University of Colorado Boulder and the National Institute of Standards and Technology.

Pikovsky noted that physics still contains fundamental mysteries and that quantum technologies provide new tools to investigate them.

What a superposition of time would look like

According to the authors’ proposal, sufficiently sensitive clocks could, under certain conditions, effectively “tick” at different rates simultaneously while remaining linked to their own quantum evolution.

In theory, the same time interval could experience both acceleration and deceleration at once.

Such an effect would represent a direct manifestation of the quantum nature of time — a phenomenon that has so far remained purely theoretical.

Why it matters

If the experiment succeeds, it would be more than just a confirmation of another exotic theory. Experimental evidence of the quantum nature of time could become an important step toward a full theory of quantum gravity, one of the biggest unresolved problems in modern physics.

For now, the idea remains a proposed experiment, but the authors are confident that rapid progress in quantum technologies could make such tests feasible in the near future.

In brief

Physicists led by Igor Pikovsky have proposed using ultra-precise ion clocks to test the hypothesis that time can exist in a quantum superposition, effectively flowing faster and slower at the same time. The study, published in Physical Review Letters, combines concepts from relativity and quantum mechanics. If experimentally confirmed, it would provide one of the most unusual insights yet into the quantum nature of time and mark a significant step toward understanding the fundamental laws of the universe.