In physics, there are few concepts as familiar or puzzling as time itself. Einstein’s theory of relativity showed that time is neither fixed nor universal. Instead, it changes depending on speed and gravity. But when scientists combine the theory of relativity with quantum mechanics, things get even weirder. Quantum theory suggests that time itself may exist in a superposition. This means that time can flow both fast and slow at the same time.
A newly published study suggests that researchers may soon be able to test this strange idea in the lab. The paper, titled “Quantum signature of proper time in photoionic clocks,” was published in the journal April 20, 2026. physical review letter. The research was led by Igor Pikovsky, an assistant professor at the Stevens Institute of Technology, in collaboration with an experimental team led by Christian Sanner of Colorado State University and Dietrich Leibfried of the National Institute of Standards and Technology (NIST).
Atomic clocks and quantum time
Researchers investigated how advanced atomic clocks can reveal hidden quantum effects related to the flow of time. Their findings suggest that the same technology being developed for next-generation clocks and quantum computers could allow scientists to investigate whether time itself behaves according to quantum rules.
In quantum mechanics, objects can exist in multiple states at the same time. This concept is famously illustrated in Schrödinger’s Cat, a thought experiment in which a cat is considered both alive and dead at the same time until it is observed. Researchers suggest similar strange things may occur over time. A clock that operates according to quantum rules can experience multiple passages of time at the same time, like a young cat and an old cat at the same time.
“Time plays very different roles in quantum theory and in relativity,” Pikovsky says. “What we show is that by combining these two concepts, we can reveal hidden quantum features of the flow of time that can no longer be explained by classical physics.”
quantum twin paradox
The theory of relativity already predicts that time passes differently depending on movement and location. Every clock measures its own flow of time. For example, a clock that moves forward at 10 m/s for 57 million years will be about 1 second slower than a stationary clock. Scientists have confirmed such effects using high-precision devices such as NIST’s aluminum-ion clock.
This phenomenon is often explained using the “twin paradox,” where one twin travels at high speed and returns younger than the other twin. New research pushes this idea further into the quantum realm.
The researchers asked whether a single clock could simultaneously experience two different time speeds while existing in a quantum superposition. According to quantum theory, it should be possible. Pikovsky and his collaborators first proposed the idea more than a decade ago, when the effect was too subtle to observe experimentally. Advances in atomic clock technology could change this.
Super cold ion clock and quantum fluctuations
The research team focused on ionic clocks, such as those being developed at NIST and Colorado State University. These devices trap single ions such as aluminum or ytterbium, cool them to temperatures close to absolute zero, and use lasers to control their quantum states.
Their analysis showed that by combining high-precision clocks with trapped-ion quantum computing techniques, it may be possible to observe previously hidden quantum properties of time.
“Atomic clocks are now so sensitive that they can detect minute differences in time caused by thermal oscillations at extremely low temperatures,” said Gabriel Sorci, a doctoral candidate at Stevens Institute of Technology and co-author of the paper. “But even in the absolute zero ground state, the ticking speed is affected only by quantum fluctuations.”
So researchers investigated an even more unusual possibility. Rather than simply cooling the atoms, they proposed manipulating the vacuum itself by creating a “squeezed state,” a quantum state in which position and velocity exhibit unusual behavior.
A ticking clock speeds up and slows down at the same time
Under these conditions, the research team found that entirely new quantum effects with time can emerge. A single clock can simultaneously tick faster and slower, and at the same time become intertwined with its own quantum motion.
Researchers now hope to demonstrate these effects experimentally.
“We have the technology to generate the necessary compression and a pathway to reach the clock accuracy needed for ionic clocks, which are the first to observe such effects,” says Colorado’s Sanner.
For Pikovsky, the broader implications are equally interesting. His previous research includes showing that quantum techniques may be able to detect single gravitons, the hypothetical particles thought to carry gravity.
“Physics, at its most fundamental level, remains full of mysteries. Quantum technologies are now giving us new tools to unravel them.”
