Physicists Find a Tiny Built-In Uncertainty in Time Itself

An international team of physicists has found that alternatives to standard quantum mechanics, known as quantum collapse models, could have consequences for the nature of time itself and for the ultimate precision of clocks. The study, led by Nicola Bortolotti, a PhD student at the Enrico Fermi Museum and Research Centre (CREF) in Rome, Italy, is published in Physical Review Research.

In standard quantum mechanics, a particle can exist in a superposition of multiple states at once, described mathematically by a wavefunction; the wavefunction is said to collapse into one definite outcome only when the system is measured. Since the 1980s, physicists have explored an alternative idea called quantum collapse models, in which the wavefunction can collapse spontaneously, without any measurement or observer. Unlike most interpretations of quantum theory, collapse models predict physical effects that could, in principle, be measured.

The team examined two such models. One, the Diosi-Penrose model, proposes that gravity itself forces quantum systems to collapse into definite states. The other, called Continuous Spontaneous Localization, was linked by the researchers for the first time to gravitational fluctuations in spacetime. Their calculations found that if these collapse models are correct, time itself should contain a small amount of intrinsic uncertainty, meaning there may be a fundamental limit to how precisely time can ever be measured.

The researchers stressed that the predicted effect is extraordinarily small. Co-author Catalina Curceanu, a research director at the Frascati National Laboratories of Italy's National Institute for Nuclear Physics, said the uncertainty is many orders of magnitude below anything scientists can currently measure. Co-author Kristian Piscicchia added that even the most advanced atomic clocks operating today, or those expected in the foreseeable future, would not be precise enough to notice the effect. The work was carried out with support from the Foundational Questions Institute (FQxI).