Physicists exploring quantum collapse models have discovered that time itself could possess a tiny built-in uncertainty, establishing a fundamental limit on clock precision. Published in Physical Review Research and supported by the Foundational Questions Institute (FQxI), the study links these theoretical models to gravity and spacetime fluctuations.
Quantum mechanics has long challenged our everyday perception of reality. In the microscopic world, particles occupy multiple positions or configurations simultaneously through a superposition of states, described mathematically by a wavefunction. While ordinary macroscopic objects appear to occupy a single place and state, standard quantum mechanics bridges this gap by stating that observation causes a wavefunction to collapse into a definite outcome. Now, an international team of physicists backed by the Foundational Questions Institute (FQxI) has explored a more radical possibility, suggesting that alternative frameworks known as quantum collapse models could impose fundamental limits on time itself.
Spontaneous Collapse Models and Gravity
Beginning in the 1980s, physicists developed models where wavefunction collapse occurs spontaneously without requiring an external measuring device or observer. Unlike standard interpretations of quantum mechanics—which offer different conceptual meanings while yielding identical experimental predictions—these collapse models predict physical effects that can, in principle, be measured. The study, published in Physical Review Research, focuses on two specific frameworks.
Researchers examined the Diósi-Penrose model, named after FQxI members Lajos Diósi and Sir Roger Penrose, which proposes that gravity plays a direct role in forcing quantum systems into definite states. The team also investigated a second approach called Continuous Spontaneous Localization. For the first time, the investigators established a quantitative connection between this second model and gravitational fluctuations in spacetime. Nicola Bortolotti, a PhD student at the Enrico Fermi Museum and Research Centre (CREF) in Rome, Italy, led the study.
Intrinsic Uncertainty in Timekeeping Technologies
The mathematical calculations carried out by the team yielded a striking conclusion: if these collapse models hold true, time contains a minute amount of intrinsic uncertainty, placing an ultimate precision ceiling on clocks. However, the researchers emphasize that this theoretical limitation has no immediate impact on human technology. The predicted disruption is exceptionally small.
Even the most advanced atomic clocks operating today, as well as those anticipated in the foreseeable future, lack the sensitivity required to detect the effect. According to Catalina Curceanu, a research director at the Laboratori Nazionali di Frascati of the National Institute for Nuclear Physics (INFN-LNF) in Frascati, Italy, and an FQxI member, the uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping.
Kristian Piscicchia of CREF and INFN-LNF adds that modern timekeeping technologies remain entirely unaffected by the phenomenon.
Reconciling Quantum Mechanics and General Relativity
This theoretical work addresses one of the biggest unsolved problems in modern physics: reconciling quantum mechanics with gravity. Quantum mechanics excels at describing microscopic systems like atoms and particles, while Einstein’s general theory of relativity successfully describes space, time, and gravity on cosmic scales involving planets, stars, and galaxies. Yet the two frameworks treat time in fundamentally incompatible ways.
In standard quantum mechanics, time functions as an external, classical parameter unaffected by studied quantum systems. Conversely, general relativity treats space and time as a flexible fabric of spacetime capable of bending and changing in response to mass and energy. This structural mismatch has driven physicists to spend decades searching for a unified theory of quantum gravity. The research team also included Simone Manti of INFN-LNF and Lajos Diósi of the Wigner Research Center for Physics and Eötvös Loránd University in Budapest, Hungary.
