New research shows that timekeeping can be exponentially more precise—without breaking the laws of physics.
Key Points at a Glance
- Quantum clocks can exceed previously assumed accuracy limits by using two distinct time scales.
- This method enables exponential accuracy growth with only linear increases in entropy.
- Findings challenge the traditional belief that more precision requires proportionally more energy.
- The theory may be tested using superconducting circuits—bringing lab validation within reach.
Quantum clocks—already among the most precise instruments in existence—may soon become dramatically more accurate, thanks to new theoretical breakthroughs from researchers at TU Wien, Chalmers University of Technology, and the University of Malta. Their findings, published in Nature Physics, reveal a novel way to sidestep an old assumption: that every increase in clock precision must be paid for in energy.
For decades, physicists believed that a clock twice as precise must use at least twice as much energy. This belief stems from the second law of thermodynamics, which links information and entropy: in simple terms, every tick of a clock must cause some irreversible physical change—an increase in disorder somewhere in the system.
But now, by cleverly separating quantum and classical processes across two scales of time measurement, researchers have shown that precision can be enhanced exponentially while only slightly increasing entropy. “It’s a bit like having a second hand and a minute hand that don’t interfere with each other,” said Prof. Marcus Huber of TU Wien. “Only one of them actually needs to generate heat and noise.”
The breakthrough relies on exploiting the strange properties of quantum particles. In their model, fast processes occur via quantum transport—particles moving through a system without being observed, and thus without generating entropy. These silent motions are not ‘real’ in the classical sense until a final measurement is made at the end of the process. That’s where entropy enters: in a single, slow, irreversible tick.
This dual-process model rewrites what we thought we knew about quantum metrology—the field that uses quantum mechanics to measure time, gravity, and other fundamental constants. Previously, clock precision was assumed to scale linearly with entropy. Now, it appears that an exponential gain is possible by pairing fast quantum evolution with sparse, delayed measurement.
“It’s like counting grains of sand through a narrow hourglass, but the grains are everywhere at once until the very last moment,” explained Florian Meier of TU Wien. “Only when one grain hits the bottom do we actually read the time—and only then do we pay the thermodynamic price.”
This new approach opens doors not just for next-generation clocks, but for a deeper understanding of time itself. By stretching the boundaries of how we measure time with minimal energy, it also sheds light on one of physics’ most mysterious frontiers: the connection between quantum mechanics and the arrow of time dictated by thermodynamics.
Excitingly, the researchers believe this theory can soon be tested in the lab using superconducting circuits—one of today’s most advanced platforms in quantum technology. “This is more than a theoretical curiosity,” said co-author Simone Gasparinetti. “It’s a design principle for building better, smarter timekeeping systems in the real world.”
Source: TU Wien
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