Beyond Science

The Quantum Watch: Swedish Physicists Find New Way to Measure Time

BY Jennifer Margulis TIMEMarch 15, 2023 PRINT

As they described in a study published in the peer-reviewed journal Physical Review Research, a team of particle physicists at the University of Uppsala, Sweden, have invented what they called a “quantum watch.”

This watch, the researchers argued, is intrinsically accurate. In fact, they contended in the study their quantum watch can measure time much more accurately than time has ever been measured before.

Time When You Get Tiny

Quantum particles are the smallest possible pieces of entity. Atoms are made up of quantum particles. The problem with measuring time at the finest scale is that you need to look at these quantum particles, and events get fuzzy at that scale.

So instead of trying to pin down hard-to-nail-down quanta, the Swedish physicists used lasers to increase the energy in atoms. This made the atoms expand. Then the physicists watched how the fields around nearby atoms overlapped each other.

In case you don’t remember Physics 101, an atom is made up of a nucleus and one or more electrons. The nucleus is positively charged. Electrons are negatively charged. The nucleus in the center of the atom is made up of electrically positive protons and electrically neutral neutrons, which are in turn made up of quarks. Electrons orbit the nucleus. Electrons, protons, and neutrons are all quantum particles.

When enough energy is put into an atom, the halo of electrons that orbit the nucleus of the atom expands, making what is called a Rydberg atom.

A Rydberg atom is an atom that has energy pumped into it, which makes the electron cloud around it expand.

You can’t watch electrons going around a nucleus because they are quantum particles that exist in a vague quantum “wave.” But the Rydberg state does make that wave take on a distinctive shape you can observe.

Patterns of Peaks and Troughs

Like waves in water, when quantum particles cross each other, they make patterns of peaks and troughs.

The Swedish scientists had the insight that the shape of the waves interfering with one another could be analyzed to reveal when each wave evolved relative to the other waves.

Two Frogs Make Waves In A Pond

Think of a still pond. A frog jumps in. The concentric circles of ripples slowly spread across the smooth surface. Once these circles have spread across most of the lake, another frog jumps in from the other side. The second frog’s ripples will be smaller circles, at first, moving against the large circles from the first frog.

Someone standing on the bank could watch the pattern and know, just by looking, that the little circles happened later than the big circles.

A physicist observing them could measure the overlapping pattern of ripples and calculate exactly how long it was between the time the first frog jumped into the still water and the second frog jumped into the still water.

That is a good analogy of what these researchers did, except instead of observing frogs, they observed the waves of electrons overlapping.

Simple, Stable Helium Atoms

The Swedish team used atoms of helium, which are simple and stable. Helium is made up of only two protons, two neutrons, and two electrons.

They excited these atoms with a laser to start the waves interfering with each other, and then observed the pattern the waves made in order to tell how “old” each wave was—just as you could theoretically measure the ripples in a pond to analyze when they were made.

Accurate Within 8 Quadrillionths Of A Second

According to the scientists, their experiment provided a time stamp accurate within 8 quadrillionths of a second. A quadrillionth is a thousand million millionths.

An atomic clock is a standard way of measuring time. It has been used by physicists for the last several decades. An atomic clock works in a completely different way. So the researchers wanted to distinguish their way of measuring time from atomic clocks, so they called their method a “watch.”

Like mechanical watches, which have a spring-wound mechanism that beats a certain number of times per second, the interference of the waves created regular “quantum beats” that could be measured in this experiment.

But don’t be confused by their linguistic choices. This experiment did not involve an actual wristwatch, and the Swedish physicists did not provide a timetable for when any of us might be able to wear a quantum watch on our wrists.

From Material to Metaphysical

Other physicists might find practical applications for this quantum watch. The rest of us, however, don’t really need to measure time quite so accurately.

But for the layperson this study is interesting because it asks us to think about time. Most of us think of time as a progression of events—something that moves forward. But Albert Einstein argued that time was relative—that the rate at which time has passed or will pass depend on one’s frame of reference.

There is also a cultural component to how we understand time. In Buddhism, for instance, life is impermanent and our human experience of time is considered an illusion.

Time, instead of being something to measure, is a way that humans unnecessarily limit themselves.

Some spiritual thinkers in America argue that we can go back in time and change events that have happened in the past by re-envisioning or re-imagining them in a different way.

The late Louise Hay, a metaphysical thinker and author of the 1984 book, “You Can Heal Your Life,” believed that while we cannot change the past, we can let go of any event that happened in the past by changing the way we think about it in the present.

Others believe that you can actually materially heal from and perhaps even change past events by reaching deep into your psyche and envisioning yourself as you were back then and imagining that what happened to you happened differently.

Can we change the past, the present, or the future? Maybe we can already. Or maybe we will be able to one day. But in the meantime, we can ponder, and celebrate, the present achievement of a team of hardworking Swedish physicists seeking to measure time on the quantum level.

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Jennifer Margulis, Ph.D., is an award-winning journalist and author of “Your Baby, Your Way: Taking Charge of Your Pregnancy, Childbirth, and Parenting Decisions for a Happier, Healthier Family.” A Fulbright awardee and mother of four, she has worked on a child survival campaign in West Africa, advocated for an end to child slavery in Pakistan on prime-time TV in France, and taught post-colonial literature to nontraditional students in inner-city Atlanta. Learn more about her at
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