Time crystals are quantum phases of matter that spontaneously oscillate, like a tuning fork with an infinitely decaying echo. If an ordinary spatial crystal repeats an atomic pattern in space, breaking translational symmetry, a time crystal exhibits periodicity in time, breaking time translation symmetry. The concept was put forward in 2012 by Frank Wilczek, who suggested the possibility of a system that moves and returns to its initial state without expending energy.
Recently, scientists have realized such states on quantum chips using precise control and measurement of qubits. The observed time crystals exhibit diverse oscillation patterns: their rhythm can be discrete (jumpy) or continuous (smooth), and also include more exotic types, such as time quasicrystals with multiple incommensurate frequencies. All this manifold has been systematized into a kind of taxonomic table — an analog of the Standard Model of elementary particles, but for time crystals. Such an ordered collective rhythm, resistant to perturbations, challenges entropy — the measure of disorder that usually drives systems toward equilibrium. This resilience links time crystals to pulsars — neutron stars whose rotation generates strictly periodic radio pulses.
The practical value lies in creating ultra-precise clocks and synchronizing quantum computations without additional energy costs. The surprise is that perpetual pulsation does not require a perpetual motion machine: the crystal merely redistributes external kicks, like a tuning fork that hums at its resonant note after a single strike, without violating the law of conservation of energy.
The first time crystal was assembled from ten laser-cooled ytterbium atoms, like a tiny orchestra with an infinite score.
As in the film 'Groundhog Day', where time is looped, time crystals exhibit cyclic behavior based on quantum laws.