Physicists built a spacetime crystal and watched it melt

Physicists have created a spacetime crystal—a novel phase of matter that repeats in both space and time—and then observed it melting, a first-of-its-kind experiment. The achievement, reported by researchers from the University of California, Riverside and the University of Chicago, marks a significant step in understanding how such exotic states behave under real-world conditions.

The spacetime crystal was built using a chain of ions (charged atoms) trapped in a magnetic field and cooled to near absolute zero. By applying precisely timed laser pulses, the team induced a pattern that oscillated in time as well as space, forming a crystal that exists in four dimensions. This structure is distinct from ordinary crystals, which repeat only in space.

The experiment matters because spacetime crystals, first proposed in 2012, challenge fundamental notions of symmetry and time. Observing their melting—the loss of temporal order—provides insights into how time-translation symmetry breaking can be disrupted, with potential implications for quantum computing and precision timekeeping.

According to the study published in *Nature Physics* on March 8, 2023, the crystal lasted for about 100 milliseconds before melting. The researchers measured the melting process by tracking the ions' quantum states, noting that the temporal order decayed gradually rather than abruptly. Lead author Dr. Kateryna Murch explained that the melting was triggered by interactions with the environment, which introduced noise and disrupted the delicate quantum coherence.

This work builds on earlier efforts to create time crystals in other systems, such as diamond impurities and superconducting qubits, but this is the first direct observation of a spacetime crystal's melting. The team now plans to explore ways to stabilize the crystal for longer periods, potentially by isolating it further from environmental disturbances. Such advances could lead to robust quantum memory devices that store information in both space and time.