A Time Crystal as a Clock
A time crystal is an exotic, out-of-equilibrium state of matter that oscillates between different configurations. The first time crystals, created in 2016, were “discrete,” a type that requires a periodic “kick” to maintain their disequilibrium. This reliance on an already-periodic signal makes discrete time crystals redundant as clocks. But researchers subsequently demonstrated “continuous” time crystals, which oscillate despite being driven by an aperiodic energy flow such as a thermal gradient or a constant beam of light. Now Ludmila Viotti from the International Centre of Theoretical Physics in Italy and colleagues have explored the timekeeping potential of such time crystals [1].
The researchers theoretically modeled a system of interacting particles that can each exist in two spin states. Energy flowing through the system causes the particles to flip from one spin state to the other. When the particles spontaneously flip back, they release detectable photons.
Although each spin flip occurs randomly, Viotti and her colleagues found that interactions between the particles cause them to cycle collectively between multiple configurations, generating a periodic burst of photons that can be used to define a clock’s “tick.” While the time between each burst varies, averaging over many bursts yields a precisely defined interval. The researchers liken this emergent precision to sand in an hourglass: The first few grains fall randomly, but as the number increases, the average fall rate converges on a predictable value. The researchers also found that the clock ticks more consistently as more particles are added, since the stronger collective behavior makes the clock more robust against noise. They say that their proposed clock could be realized using a cloud of cold atoms and could illuminate the thermodynamic constraints on clock precision.
–Sophia Chen
Sophia Chen is a freelance science writer based in Columbus, Ohio.
References
- L. Viotti et al., “Quantum time crystal clock and its performance,” Phys. Rev. Lett. 136, 110401 (2026).