Here’s what you’ll learn when you read this story:

• In Albert Einstein’s Special Theory of Relativity, the concept of “time dilation” illustrates that the flow of time is dependent on the velocity and position of the observer.
• In the quantum world, time has an even more counterintuitive behavior known as the “quantum twin paradox,” which describes how time can move both fast and slow in superposition.
• Using ultraprecise atomic clocks, along with technologies developed from trapped-ion quantum computing, scientists are getting close to experimentally testing the quantum realities of time itself.

To those of us living on Earth, time appears relatively immutable. Except for some clever bits of human intervention, one second inexorably ticks by after another in a never-ending march. But in the extreme worlds of general relativity and quantum theory, time is anything but constant.

In the early 20th century, Albert Einstein first demonstrated the concept of “time dilation”—where time flows differently based on the velocity and position of the observer—with his theory of special relativity. The most common example is that if you were to propel yourself near the speed of light, time (at least, from your perspective) would stop. While this is mind-bending enough as-is, quantum mechanics counters this oddity with a real “hold my beer” moment of its own. According to physicists, it’s theoretically possible for time itself to be in quantum superposition, meaning it can both flow quickly and slowly at the same time.

Now, actually testing this theory isn’t easy. But a new study—led by scientists at the Stevens Institute of Technology, the National Institute of Standards and Technology (NIST), and Colorado State University—argues that it just might be possible. The key is the use of ultraprecise atomic clocks coupled with quantum information technology developed for trapped-ion quantum computing. Together, the team argues, these technlogies could reveal new characteristics of time at the quantum level. The results of the study were published in the journal Physical Review Letters.

“Time plays very different roles in quantum theory and in relativity,” Igor Pikovski, senior author of the study from Stevens Institute of Technology, said in a press statement. “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.”

The idea is known as the “quantum twin paradox.” Using the illustration of everyone’s favorite quantum cat, theoretical physicist Erwin Schrödinger demonstrated that something could be in two completely different states at the same time before a measurement could be performed. This is known as superposition, and if we extrapolate this idea to the realm of time, not only could Schrödinger’s cat be both alive and dead, it could also be both old and young.

Pikovski has been on the hunt to prove this quantum weirdness for more than 15 years, and now believes that the advent of ultraprecise atomic clocks might just be the answer. Using trapped-ion clocks developed by NIST and Colorado State University—which rely on freezing aluminum or ytterbium to near-absolute zero in order to manipulate their quantum state with lasers—and controlling the vacuum surrounding the atoms they were observing, the team created what they call a “squeezed state.” This, theoretically, should allow the clock to reveal new behaviors of relativistic time in the quantum world, possibly opening the door to experimental verification of the “quantum twin paradox.”

“I think it can give us hints, and experimental input, on how our everyday notions of reality are misleading,” Pikovski told Science Alert. “Quantum theory is not just bizarre, it also implies a very different fundamental structure of the universe that is at odds with everyday experience.”