Quantum mechanics has long challenged our everyday understanding of reality, forcing physicists and philosophers alike to rethink the very nature of existence. In the peculiar subatomic domain, particles can exist in what is known as a superposition of states, meaning they can occupy multiple possible positions, energy levels, or configurations simultaneously. To describe these nebulous possibilities mathematically, physicists rely on a conceptual tool called a wavefunction.
This counterintuitive picture stands in stark contrast to ordinary life, where everyday objects like chairs, tables, and planets appear firmly anchored in one place and one state at any given moment. To bridge that vast conceptual gap between the microscopic and macroscopic worlds, standard quantum mechanics dictates that when a quantum system is measured, interacted with, or observed by an external device, its wavefunction abruptly collapses into a single, definite outcome.
Now, with vital support from the Foundational Questions Institute (FQxI), an international team of theoretical and experimental physicists has explored a much more radical possibility. Their groundbreaking work suggests that certain alternatives to standard quantum mechanics—known collectively as quantum collapse models—could have surprising, profound consequences for the fundamental nature of time itself and for the ultimate precision of clocks.
The findings, which have been published in the peer-reviewed journal Physical Review Research, also point toward a potential new pathway to test these unconventional theories against the bedrock predictions of standard quantum mechanics.
"What we did was to take seriously the idea that collapse models may be linked to gravity," says Nicola Bortolotti, a PhD student at the Enrico Fermi Museum and Research Centre (CREF) in Rome, Italy, who led the new study. "And then we asked a very concrete question: What does this imply for time itself?"
When Quantum States Collapse on Their Own
The roots of this investigation trace back to the 1980s, when pioneering physicists began developing theoretical models in which wavefunction collapse does not rely on an external measuring device or a conscious observer. Instead of requiring human intervention or laboratory apparatuses to force a definite state, collapse can happen spontaneously all on its own as a natural feature of physical law.
This characteristic sets these alternative ideas apart from many traditional interpretations of quantum mechanics. While standard interpretations primarily offer different conceptual explanations for what quantum theory actually means while yielding the exact same experimental predictions as standard quantum mechanics, quantum collapse models go significantly further. They predict distinct physical effects that could, at least in principle, be detected and measured in advanced laboratories.
Bortolotti and his colleagues closely examined two different collapse models during their research. The collaborative team included Catalina Curceanu, a member of FQxI and research director at the Laboratori Nazionali di Frascati of the National Institute for Nuclear Physics (INFN-LNF) in Frascati, Italy; Kristian Piscicchia, based at CREF and INFN-LNF; Lajos Diósi, of the Wigner Research Center for Physics and Eötvös Loránd University in Budapest, Hungary; and Simone Manti of INFN-LNF.
One of the prominent frameworks they evaluated was the Diósi-Penrose model, named jointly after FQxI members Lajos Diósi and legendary physicist Sir Roger Penrose. This model has long proposed that gravity itself may play a direct, active role in forcing quantum systems to abandon their superpositions and collapse into definite states.
Alongside that approach, the researchers also studied a second major framework known as Continuous Spontaneous Localization. For the very first time in the history of these models, the team established a rigorous quantitative connection between that specific localization model and natural gravitational fluctuations rippling through spacetime.
Time May Have a Tiny Built-In Uncertainty
The mathematical calculations carried out by the team led to a striking and unexpected conclusion. If these spontaneous collapse models accurately describe the physical world, then time itself should contain a vanishingly small amount of intrinsic uncertainty.
In practical terms, this implies there may be a fundamental, unyielding limit to how precisely time can ever be measured in our universe. However, the researchers emphasize that this theoretical restriction does not mean our most reliable clocks are suddenly about to become unreliable or erratic. The predicted physical effect is extraordinarily minuscule.
"Once you do the calculation, the answer is clear and surprisingly reassuring," Bortolotti noted regarding the implications of their mathematical models.
Even the most advanced, ultra-precise atomic clocks operating in laboratories today, as well as any next-generation timing devices expected to be developed in the foreseeable future, would not possess nearly enough sensitivity to notice the effect directly.
"The uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping," explains Curceanu, highlighting the scale of the phenomenon. "Our results explicitly show that modern timekeeping technologies are entirely unaffected," adds Piscicchia, reinforcing the stability of our current technological standards.
A Possible Clue to Quantum Gravity
Beyond timekeeping, the new research touches directly upon one of the most stubborn and enduring unsolved problems in modern physics: how to successfully reconcile quantum mechanics with the laws of gravity.
Quantum mechanics has proven to be enormously and repeatedly successful at describing atoms, subatomic particles, and other microscopic systems with astonishing precision. Meanwhile, Albert Einstein’s general theory of relativity successfully describes gravity and the smooth behavior of space and time on much larger scales, governing everything from orbiting planets and massive stars to distant galaxies and the large-scale structure of the universe itself.
Both foundational theories agree extremely well with physical experiments within the respective domains where they are applied. The fundamental crisis lies in the fact that they treat time in radically different, incompatible ways.
"In standard quantum mechanics, time is treated as an external, classical parameter that is not affected by the quantum system being studied," Curceanu explains, describing the traditional view.
General relativity, on the other hand, takes a fundamentally different view of reality. Within Einstein’s framework, space and time are inextricably linked into a flexible, dynamic four-dimensional structure called spacetime, which actively bends, warps, and changes in response to the presence of mass and energy.
Because of this deep theoretical mismatch, physicists have spent decades searching for a deeper, overarching theory of quantum gravity that could successfully unite quantum mechanics and gravity into a single coherent picture. The new research results suggest that spontaneous collapse models may hold vital clues about how quantum physics, gravity, and time could ultimately fit together.
Furthermore, the work offers a practical benefit for experimental physics. Because collapse models predict measurable deviations that theoretically differ from standard quantum mechanics, extremely precise future experiments could eventually help determine whether these unconventional ideas describe actual physical phenomena in nature.
Curceanu emphasized the critical importance of continuing to support rigorous research into unconventional questions situated at the deep foundations of modern physics.
"There are not many foundations in the world which are supporting research on these types of fundamental questions about the universe, space, time, and matter," says Curceanu. "Our work shows that even radical ideas about quantum mechanics can be tested against precise physical measurements, and that, reassuringly, timekeeping remains one of the most stable pillars of modern physics."
This work was partially supported through FQxI’s Consciousness in the Physical World program.
