In 2012, Nobel laureate Frank Wilczek asked whether the symmetry that arranges atoms in an ordinary crystal might also break in time, producing a structure that beats forever at its own pace.
More than a decade later, researchers at Tsinghua University, working with theorists from Vienna University of Technology, have watched rubidium vapor settle into just such a rhythm and report their findings.
Prof Thomas Pohl of the Institute of Theoretical Physics at TUWien, a coauthor of the new paper, says the result brings Wilczek’s vision “very close to reality.”
—
How a time crystals differ
A time crystal repeats itself in time rather than in space, breaking the uniformity of the clock the way a snowflake breaks the uniformity of a lake.
The persistence of this rhythm, called spontaneous symmetry breaking, means the pattern survives even when no one is forcing it.
Laboratory evidence has grown fast, from early iontrap demonstrations of discrete time crystals in 2017 to opticalcavity work that showed continuous versions in 2022.
Yet every platform had limits, such as ultracold temperatures or brief lifetimes, that left physicists wanting a clearer test bed.
The new rubidium system operates at room temperature and runs for hundreds of milliseconds at a time, long enough to watch thousands of oscillations.
That endurance turns the humble glass cell into a laboratory for fundamental questions about nonequilibrium phases of matter.
“The tick frequency is predetermined by the physical properties of the system, but the times at which the tick occurs are completely random,” Pohl notes. The statement underscores that the crystal’s clock sets itself, with no hidden conductor waiting in the wings.
—
Possible applications and open questions
The vaporcell crystal also offers a living classroom for nonequilibrium thermodynamics, showing how systems trade energy and entropy while holding a strict temporal pattern.
Lessons learned here could inform models of rhythmic behavior in chemical reactions, biological clocks, and even economic cycles.
Engineers eyeing quantum networks wonder whether time-crystal phases can synchronize remote nodes through shared photons, reducing the overhead for entangling operations.
The long-range Rydberg interactions and optical accessibility make the rubidium platform an attractive test case.
Still unresolved is whether a truly dissipation-free, closed-system time crystal can exist, or whether some coupling to an environment is always needed to stabilize the beat. The present work, like most others, relies on a balance of drive and loss.
Another question is how quantum coherence, rather than classical population oscillations, manifests in a macroscopic continuous time crystal. Experiments coupling Rydberg media to highfinesse cavities may soon probe that regime.
h/t Sands_of_the_Hourglass