Science1 publisher2 min readPublished
Rome group turns two collapse models into a limit on how precisely any clock can run
A team supported by the Foundational Questions Institute calculated what two spontaneous collapse models imply for time and found an intrinsic uncertainty in it, many orders of magnitude below what today's atomic clocks can measure.
The Scientist · Science desk
What happened
- An international team working with support from the Foundational Questions Institute published a calculation in Physical Review Research on what spontaneous collapse implies for time.
- Their conclusion is that if those collapse models are correct, time carries a very small intrinsic uncertainty, setting a fundamental limit on how precisely it can be measured.
- The authors present the calculation as a possible new route to testing collapse models against standard quantum mechanics.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint The predicted limit is not a number any metrology lab will design against. It sits so far under current sensitivity that clock data can only bound the collapse parameters.
- capability Collapse models differ from interpretations of quantum mechanics by predicting effects that can in principle be measured, so a time-uncertainty prediction adds one more observable that experimenters can try to squeeze.
- contradiction The release is headlined as physicists finding a glitch in time, while its own text describes a conditional calculation whose effect nobody can measure. Readers who stop at the headline will take a theoretical if-then for an observation.
- decision Anyone deciding where to hunt for this has nothing to work from yet: with no published size or scaling for the uncertainty, there is no basis for choosing between a clock, an interferometer or a mechanical oscillator.
Of the two ideas the calculation rests on, only one is new. The Diosi-Penrose model, named for Lajos Diosi and Roger Penrose, has long proposed that gravity plays a role in forcing quantum systems to collapse into definite states [4]. Continuous Spontaneous Localization does not start from gravity, and the quantitative connection the group established between that model and gravitational fluctuations in spacetime is, according to the FQXi account, the first of its kind [5]. From there the calculation gives time itself a very small intrinsic uncertainty, and with it a limit on how precisely time can ever be measured [6].
"What we did was to take seriously the idea that collapse models may be linked to gravity," said Nicola Bortolotti, the PhD student at Rome's Enrico Fermi Museum and Research Centre who led the study [2][7]. "Once you do the calculation, the answer is clear and surprisingly reassuring," he said [8].
A clock could register this only if the predicted uncertainty exceeded the clock's own instability, and it is nowhere near that. Catalina Curceanu, research director at INFN's Frascati laboratory, said the uncertainty "is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping" [3][9]. Kristian Piscicchia added that "Our results explicitly show that modern timekeeping technologies are entirely unaffected" [10]. The release says neither today's best atomic clocks nor those expected in the foreseeable future would be precise enough to notice the effect [11].
A reader cannot rank candidate experiments by how close any of them gets. The release gives no figure for the predicted uncertainty, and no scaling with mass, averaging time or clock design.
Interpretations of quantum mechanics mostly offer different conceptual accounts while reproducing the same experimental predictions; collapse models, developed from the 1980s onward with collapse happening spontaneously and without an observer, predict physical effects that could in principle be measured [12][13]. This paper computes one such effect on the assumption that the models hold. No measurement was performed.
Read in the other direction, the relation is more useful in the near term. A clock comparison that sees nothing puts an upper limit on the collapse parameters, and given that the predicted effect sits many orders of magnitude below current sensitivity, that limit is what a clock test would return [14]. The authors present the result as a possible new way to test these theories against standard quantum mechanics [15].
What to watch
- The published paper's scaling law: whether the predicted uncertainty grows with mass or averaging time decides which experiment gets closest.
- Whether other groups reproduce the quantitative link between Continuous Spontaneous Localization and gravitational fluctuations, which is the new step here.
- Whether any group converts the prediction into a published upper bound on collapse-model parameters using existing clock or interferometer data.