# Quantum time crystals open up

@article{Ball2021QuantumTC, title={Quantum time crystals open up}, author={Philip Ball}, journal={Nature Materials}, year={2021}, volume={20}, pages={1172 - 1172} }

Time crystals are a temporal analogue of ordinary ‘space’ crystals: many-body systems that are periodic not in space but in time. They evolve dynamically in a way that regularly returns to a particular configuration. After these curious entities were proposed by Wilczek1 in 2012, the question became: what manner of system might behave this way? On closer inspection, it became clear that such behaviour is not possible for the equilibrium ground state of any system2,3 — time crystals are possible…

## One Citation

### Criticality and rigidity of dissipative discrete time crystals in solids

- PhysicsPhysical Review Research
- 2022

We consider a dissipative quantum Ising model periodically driven by a train of π-pulses and investigate dissipative discrete time crystals (DTCs) in solids. In this model, the interaction between…

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A no-go theorem is proved that rules out the possibility of time crystals defined as such, in the ground state or in the canonical ensemble of a general Hamiltonian, which consists of not-too-long-range interactions.

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The experimental observation of a discrete time crystal, in an interacting spin chain of trapped atomic ions, is presented, which opens the door to the study of systems with long-range spatio-temporal correlations and novel phases of matter that emerge under intrinsically non-equilibrium conditions.

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This work provides a simple and pedagogical framework by which to obtain many-body time crystals using parametrically coupled resonators and presents a clear distinction between single-mode time-translation symmetry breaking and a situation where an extensive number of degrees of freedom undergo the transition.

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A phenomenology of dissipative discrete time crystals is established by generalizing the Landau theory of phase transitions to Floquet open systems and finding clear signatures of a transient discrete time-crystalline behavior, which is absent in the isolated counterpart.

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This work observes long-lived temporal correlations, experimentally identifies the phase boundary and finds that the temporal order is protected by strong interactions, which opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems.

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The Dicke model—a paradigmatic example of superradiance in quantum optics—describes an ensemble of atoms which are collectively coupled to a leaky cavity mode. As a result of the cooperative nature…

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We propose the dynamical stabilization of a nonequilibrium order in a driven dissipative system comprised an atomic Bose–Einstein condensate inside a high finesse optical cavity, pumped with an…

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The dissipative Dicke model exhibits a fascinating out-of-equilibrium many-body phase transition as a function of a coupling between a driven photonic cavity and numerous two-level atoms. We study…

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The first experimental realization of a time crystal stabilized by dissipation is presented, demonstrating the robustness of this dynamical phase against system parameter changes and temporal perturbations of the driving.

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Some subtleties and apparent difficulties associated with the notion of spontaneous breaking of time-translation symmetry in quantum mechanics are identified and resolved. A model exhibiting that…