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What are time crystals? 


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Time crystals are nonequilibrium many-body phases in which the state of the system dynamically approaches a limit cycle. These phases have been the focus of intensive research, but it is still unclear whether they can host quantum correlations. Mostly classical correlations have been observed so far, suggesting that time crystals are effectively classical high-entropy phases . Photonic Time Crystals (PTCs) are dielectric media with a periodically modulated refractive index. They exhibit momentum bands and bandgaps, where the amplitudes of their eigenmodes can exponentially increase or decrease. PTCs have potential applications in making widely tunable lasers that extract energy from the temporal modulation of the medium . Recent experimental work has observed the emergence of a prethermal time crystalline state at quasi-infinite temperature in a solid-state NMR quantum emulator. This state exhibits period-doubling behavior and long-range correlations, ruling out many-body localization .

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Time crystals are dielectric media that have a periodically modulated refractive index at time scales of an optical cycle. They conserve momentum but not energy and have momentum bands and bandgaps.
Open accessPosted ContentDOI
17 Mar 2023
Time crystals are states of matter that break discrete time translation symmetry and can exhibit intriguing and robust properties absent in equilibrium systems.
Time-crystals are nonequilibrium many-body phases in which the state of the system dynamically approaches a limit cycle.
Time crystals are materials in which the refractive index varies periodically and abruptly in time, exhibiting unusual properties such as momentum bands and gaps for wave amplification.
Time-crystals are nonequilibrium many-body phases in which the state of the system dynamically approaches a limit cycle.

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