The strange quantum nature of time moves one step closer to being untangled, thanks to new research on optical ion clocks that could allow scientists to test the flow of time in a new way.
Since Albert Einstein first presented his theory of relativity, scientists have known that the flow of time is not absolute. Yet quantum theory takes this further, suggesting that time may exist in a superposition, flowing both slower and faster concurrently, not being set until it is measured.
Now, a research team from the Stevens Institute of Technology, Colorado State University, and the National Institute of Standards and Technology (NIST) has published a paper in Physical Review Letters describing how optical ion clocks could be used to evaluate whether time itself can exist in a quantum superposition.
Atomic Clocks and Quantum Time
In an atomic clock, the device is tuned to the steady vibration of an atom, which acts as a natural metronome, keeping time with extraordinary precision. Thanks to their stability and accuracy, atomic clocks underpin GPS and global communications systems, ensuring that everything is precisely synchronized. Now, researchers are exploring how that same precision might be applied at the quantum level.
These clocks rely on motion—the vibration of an atom. Yet in quantum theory, motion itself can exist in a superposition, remaining uncertain until it is measured. This makes atomic clocks a promising tool for investigating whether the same uncertainty applies to the flow of time.
“Time plays very different roles in quantum theory and in relativity,” said co-author Igor Pikovski, Assistant Professor of theoretical physics at Stevens Institute of Technology. “What we show is that bringing these two concepts together can reveal hidden quantum signatures of time-flow that can no longer be described by classical physics.”
Quantum Relativity
Relativity shows that time is not absolute or independent, but instead depends on the clock measuring it. Velocity and position are key factors that determine how quickly time passes relative to a given observer. For example, a clock moving at a different speed will experience time differently—a phenomenon confirmed by atomic clock experiments.
This idea is often illustrated by the twin paradox: if one identical twin travels at high speed while the other remains on Earth, they will age at different rates. In quantum theory, however, this concept gives rise to the so-called quantum twin paradox, in which a single system can experience multiple timelines simultaneously in a superposition. While this idea is theoretically sound, experimental tests have remained out of reach with current technology.
Atomic Clocks and Relativity
In their new research, the team demonstrated that combining advanced atomic clock technology with quantum computing techniques could enable quantum time research.
“Atomic clocks are now so sensitive, they can detect tiny differences in time caused by just the thermal vibrations at minuscule temperatures,” said co-author Gabriel Sorci, a PhD candidate at Stevens Institute of Technology. “But even at the absolute zero temperature, the ground state, the ticking rate will still be affected by just the quantum fluctuations alone.”
The researchers showed that cooling techniques used in quantum computing can produce so-called squeezed states, where quantum behavior becomes detectable within the clock. In theory, this could allow a single clock to measure time as both faster and slower simultaneously.
“Physics is still full of mysteries at the most fundamental level,” Pikovski concluded, adding that “Quantum technologies are now giving us new tools to shed light on them.”
The paper, “Quantum Signatures of Proper Time in Optical Ion Clocks,” appeared in Physical Review Letters on April 20, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.