Will the quantum superposition of time soon be tested in a laboratory?

Amazing stuff! Food for thought! Can time run simultaneously faster and slower?

"Trapped ions are versatile platforms used for quantum computing and ultra-precise timekeeping. New results now show that combining these capabilities can reveal a deeper layer of physical reality: quantum superpositions of the passage of time. ...

Few concepts in physics are as familiar, yet as enigmatic, as time.

In Einstein’s theory of relativity, time is not absolute: its passage depends on motion and gravity.

But when combined with quantum physics, this relativistic form of time becomes even more counterintuitive. According to quantum theory, the flow of time itself may exist in a genuine quantum superposition, ticking faster and slower at the same time. ...

Now, a new paper titled Quantum signatures of proper time in optical ion clocks, published on April 20, 2026 in Physical Review Letters ... shows that this striking possibility may soon be tested in the laboratory. ...

In this work, a team ... explores quantum aspects of the flow of time and how they can be accessed with atomic clocks. Their results suggest that the same quantum technologies being developed for next-generation clocks and quantum computers may soon probe something far more fundamental: When a clock’s motion obeys quantum mechanics, its movement can exist in superposition, and with it the recorded passage of time itself.

This is analogous to Schrödinger’s famous thought experiment, where the counterintuitive nature of quantum superposition is illustrated by a cat being both alive and dead; here it is the passage of time itself that is in superposition, like a cat that is both young and old at once. ..."

From the abstract:

"Optical clocks based on atoms and ions probe relativistic effects with unprecedented sensitivity.

They resolve time dilation due to atom motion or different positions in the gravitational potential through frequency shifts. However, all measurements of time dilation so far can be explained effectively as the result of dynamics with respect to a classical proper time parameter.

Here we show that atomic clocks can probe effects where a classical description of the proper time dynamics is insufficient as superpositions of proper time emerge.

We apply a Hamiltonian formalism to derive time dilation effects in harmonically trapped clock atoms and show how second-order Doppler shifts due to the vacuum energy, squeezing, and quantum corrections to the dynamics arise.

We also demonstrate that time-dilation-induced entanglement between motion and clock evolution can become observable in state-of-the-art clocks when the motion of the atoms is strongly squeezed, realizing proper time interferometry.

Our results show that experiments with trapped ion clocks are within reach of probing relativistic evolution of clocks for which a quantum description of proper time becomes necessary."

Scientists at Stevens Institute of Technology Reveal That Time Can Go Quantum in Ion Clock Experiments "Physicists show that atomic clocks can probe time ticking both faster and slower simultaneously, revealing how time itself unfolds in quantum superposition"

Quantum Signatures of Proper Time in Optical Ion Clocks (open access)

Credits: Einstein trifft Quantenphysik: Wenn Zeit gleichzeitig schneller und langsamer läuft "Physiker testen ein radikales Szenario: Zeit könnte gleichzeitig schneller und langsamer vergehen. Atomuhren machen es prüfbar."

Illustration of classical, semiclassical, and quantum proper time dynamics of a trapped-ion atomic clock that we consider. 

Illustration of time-dilation-induced entanglement between clock and motional degrees of freedom, and how it can be observed using trapped atomic clocks with squeezing of motional states. The protocol proceeds from left to right.

The top row shows the motional states in a phase-space representation, where a squeezed state is prepared which then evolves at different frequencies in superposition, depending on the internal clock states.

The bottom row shows the same sequence from the perspective of the clock degrees of freedom represented on a Bloch sphere, where a Ramsey sequence results in a superposition of different time evolutions of the clocks due to the different motional energies.

The entanglement between motion and clock (last column) causes a reduction in visibility of the clock ... which can be measured with current state-of-the-art ion clock systems.

Creating the first sea-worthy navigation timepiece that accelerated ocean exploration

Recommendable!

Nuclear spectroscopy breakthrough could rewrite the fundamental constants of nature. From atomic to nuclear clocks

Good news! Exact and accurate chronometry has come a long way!

I wish physicists would not have this annoying habit of using all these special symbols you can not find on your computer keyboard!

"Key takeaways

• Raising the energy state of an atom’s nucleus using a laser, or exciting it, would enable development of the most accurate atomic clocks ever to exist. This has been hard to do because electrons, which surround the nucleus, react easily with light, increasing the amount of light needed to reach the nucleus.
• By causing the electrons to bond with fluorine in a transparent crystal, ...  physicists have finally succeeded in exciting the neutrons in a thorium atom’s nucleus using a moderate amount of laser light.
• This accomplishment means that measurements of time, gravity and other fields that are currently performed using atomic electrons can be made with orders of magnitude higher accuracy.

...
The achievement would allow today’s atomic clocks to be replaced with a nuclear clock that would be the most accurate clock to ever exist ...
This means that measurements of time, gravity and other fields that are currently performed using atomic electrons can be made with orders of magnitude higher accuracy. The reason is that atomic electrons are influenced by many factors in their environment, which affects how they absorb and emit photons and limits their accuracy. Neutrons and protons, on the other hand, are bound and highly concentrated within the nucleus and experience less environmental disturbance. ...

propose a series of experiments to stimulate thorium-229 nuclei doped into crystals with a laser, and has spent the past 15 years working to achieve the newly published results.  ...

The ... team embedded thorium-229 atoms within a transparent crystal rich in fluorine. Fluorine can form especially strong bonds with other atoms, suspending the atoms and exposing the nucleus like a fly in a spider web. The electrons were so tightly bound with the fluorine that the amount of energy it would take to excite them was very high, allowing lower energy light to reach the nucleus. The thorium nuclei could then absorb these photons and re-emit them, allowing the excitation of the nuclei to be detected and measured. By changing the energy of the photons and monitoring the rate at which the nuclei are excited, the team was able to measure the energy of the nuclear excited state. ..."

From the abstract:

"LiSrAlF6 crystals doped with 229 Th are used in a laser-based search for the nuclear isomeric transition. Two spectroscopic features near the nuclear transition energy are observed. The first is a broad excitation feature that produces redshifted fluorescence that decays with a timescale of a few seconds. The second is a narrow, laser-linewidth-limited spectral feature at 148.382 19⁢(4)stat⁢(20)sys  nm [2⁢020 407.3⁢(5)stat⁢(30)sys  GHz] that decays with a lifetime of 568⁢(13)stat⁢(20)sys  s. This feature is assigned to the excitation of the 229 Th  nuclear isomeric state, whose energy is found to be 8.355 733⁢(2)stat⁢(10)sys  eV in 229  Th :LiSrAlF6."

Nuclear spectroscopy breakthrough could rewrite the fundamental constants of nature | UCLA The findings could unlock the most accurate clock ever and allow advances like deep space navigation, communication

Laser Excitation of the 229 Th Nuclear Isomeric Transition in a Solid-State Host (no public access)

When trapped in a transparent, flourine-rich crystal, scientists can use a laser to excite the nucleus of a thorium-229 atom.

What time is it on the Moon the first colonizers may ask?

Have you ever wondered? Will the time on the dark side of the moon be different? When is it time for tea? 😊 

Do we need weather stations on the moon too? (just kidding, but who knows)

"The coming decade will see a resurgence in lunar exploration — including dozens of missions and plans to establish permanent bases on the Moon. The endeavours pose myriad challenges. Among them is a subtle, but fundamental, question that metrologists worldwide are working to answer: what time is it on the Moon? ..."

What time is it on the Moon? Satellite navigation systems for lunar settlements will require local atomic clocks. Scientists are working out what time they will keep.

Physicists harness quantum “time reversal” to measure vibrating atoms. Side effect: most accurate atomic clock ever

Amazing stuff!

"... In a paper ... the team demonstrates that the technique, which they dubbed SATIN (for signal amplification through time reversal), is the most sensitive method for measuring quantum fluctuations developed to date. ...
The technique could improve the accuracy of current state-of-the-art atomic clocks by a factor of 15, making their timing so precise that over the entire age of the universe the clocks would be less than 20 milliseconds off.
The method could also be used to further focus quantum sensors that are designed to detect gravitational waves, dark matter, and other physical phenomena. ...

For their new study, the team studied 400 ultracold atoms of ytterbium ... They cooled the atoms to just a hair above absolute zero ...

The team used a system of lasers to trap the atoms, then sent in a blue-tinged “entangling” light, which coerced the atoms to oscillate in a correlated state. They let the entangled atoms evolve forward in time, then exposed them to a small magnetic field, which introduced a tiny quantum change, slightly shifting the atoms’ collective oscillations.

Such a shift would be impossible to detect with existing measurement tools. Instead, the team applied time reversal to boost this quantum signal. To do this, they sent in another, red-tinged laser that stimulated the atoms to disentangle, as if they were evolving backward in time.

They then measured the particles’ oscillations as they settled back into their unentangled states, and found that their final phase was markedly different from their initial phase — clear evidence that a quantum change had occurred somewhere in their forward evolution. ..."

From the abstract:

"Linear quantum measurements with independent particles are bounded by the standard quantum limit, which limits the precision achievable in estimating unknown phase parameters. The standard quantum limit can be overcome by entangling the particles, but the sensitivity is often limited by the final state readout, especially for complex entangled many-body states with non-Gaussian probability distributions. Here, by implementing an effective time-reversal protocol in an optically engineered many-body spin Hamiltonian, we demonstrate a quantum measurement with non-Gaussian states with performance beyond the limit of the readout scheme. This signal amplification through a time-reversed interaction achieves the greatest phase sensitivity improvement beyond the standard quantum limit demonstrated to date in any full Ramsey interferometer. These results open the field of robust time-reversal-based measurement protocols offering precision not too far from the Heisenberg limit. Potential applications include quantum sensors that operate at finite bandwidth, and the principle we demonstrate may also advance areas such as quantum engineering, quantum measurements and the search for new physics using optical-transition atomic clocks."

Physicists harness quantum “time reversal” to measure vibrating atoms | MIT News | Massachusetts Institute of Technology A new technique could improve the precision of atomic clocks and of quantum sensors for detecting dark matter or gravitational waves.

Time-reversal-based quantum metrology with many-body entangled states (no public access)