To account for this, standard quantum theory assumes that when a quantum system interacts with a measuring device or an observer, its wavefunction suddenly collapses into a single, definite state. An international team supported by the Foundational Questions Institute FQxI has now explored a family of alternative quantum collapse models and shown that they have unexpected implications for the nature of time and for the ultimate precision of clocks.
In the 1980s, physicists began developing models in which wavefunction collapse happens spontaneously, without any need for observation or measurement. Unlike interpretations of quantum mechanics that leave experimental predictions unchanged, these quantum collapse models lead to concrete, testable deviations from standard quantum theory.
"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 study. "And then we asked a very concrete question: What does this imply for time itself?"
Bortolotti and colleagues examined two prominent collapse models. One is the Diosi Penrose model, named after Lajos Diosi and Sir Roger Penrose, which has long suggested a connection between gravity and wavefunction collapse. The other is the Continuous Spontaneous Localization model, and the team has now established a quantitative link between this model and gravitational spacetime fluctuations.
Their calculations show that if these collapse models are correct, then time itself must exhibit a tiny intrinsic uncertainty. This built in fuzziness in time translates into a fundamental, though extremely small, limit on how precisely any clock can measure time.
"Once you do the calculation, the answer is clear and surprisingly reassuring," says Bortolotti. The predicted uncertainty is far below the sensitivity of current or foreseeable timekeeping technologies.
As a result, there is no need to worry about practical consequences for wristwatches or even the most advanced atomic clocks. "The uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping," says 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. "Our results explicitly show that modern timekeeping technologies are entirely unaffected," adds co author Kristian Piscicchia of CREF and INFN LNF.
Physicists have long sought a unified framework that brings together quantum mechanics and gravity. Quantum theory governs the microscopic realm of subatomic particles, while Einstein's general theory of relativity describes gravity and the large scale structure of spacetime, from stars and galaxies to the universe as a whole.
The two theories treat time in very different ways. In standard quantum mechanics, time appears as an external, classical parameter that is not influenced by the quantum system under study. In general relativity, by contrast, time and space form a dynamical spacetime fabric that bends and warps in response to mass and energy.
By exploring collapse models that connect quantum behaviour to spacetime fluctuations, the new work hints that quantum mechanics may be just one part of a deeper theoretical structure. In this view, subtle quantum gravitational effects could underlie both wavefunction collapse and the tiny intrinsic uncertainty in time.
"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, highlighting the role of FQxI in backing unorthodox approaches. "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."
The study, "Fundamental limits on clock precision from spacetime uncertainty in quantum collapse models," was published in Physical Review Research in November 2025.
Research Report:Fundamental limits on clock precision from spacetime uncertainty in quantum collapse models
Related Links
Foundational Questions Institute FQxI
Understanding Time and Space
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