Quantum Time Crystals are not the same as the objects described in the book Time Crystals by Wyken Seagrave, although there are some similarities. To avoid confusion, we normally refer to Wyken’s time crystals by their scientific name of Chronoclastite (often shortened to Chronclast).

The articles described here are quantum time crystals. They are typically very small and only exist under very special circumstances, such as a row of ions kept out of equilibrium by being repeatedly hit with lasers. Because the spins interacted, the atoms settled into a stable, repetitive pattern of spin flipping that defines a crystal.

Chroclast, on the other hand, looks superficially like quartz except for the fact that it glows with a pale blue light although is not radioactive. Not visible to the naked eye, however, and different from any other crystal, are the negative energy strings that connect each cronclast to two others.

References to Quantum Time Crystal

Below we list some of the main references to scientific articles on quantum time crystals.

Original Proposal

ABSTRACT
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 phenomenon is displayed. The possibility and significance of breaking of imaginary time-translation symmetry is discussed.

By Frank Wilczek, Center for Theoretical Physics Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

Paper received 29 March 2012 and published 15 October 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.160401

© 2012 American Physical Society

Article Describing How to Create Discrete Time Crystals

Article entitled Discrete Time Crystals: Rigidity, Criticality, and Realizations by N. Y. Yao, A. C. Potter, I.-D. Potirniche, and A. Vishwanath, published 18 January 2017 in Phys. Rev. Lett. 118, 030401.

ABSTRACT
Despite being forbidden in equilibrium, spontaneous breaking of time translation symmetry can occur in periodically driven, Floquet systems with discrete time-translation symmetry. The period of the resulting discrete time crystal is quantized to an integer multiple of the drive period, arising from a combination of collective synchronization and many body localization. Here, we consider a simple model for a one-dimensional discrete time crystal which explicitly reveals the rigidity of the emergent oscillations as the drive is varied. We numerically map out its phase diagram and compute the properties of the dynamical phase transition where the time crystal melts into a trivial Floquet insulator. Moreover, we demonstrate that the model can be realized with current experimental technologies and propose a blueprint based upon a one dimensional chain of trapped ions. Using experimental parameters (featuring long-range interactions), we identify the phase boundaries of the ion-time-crystal and propose a measurable signature of the symmetry breaking phase transition.

Report of Observation of a Discrete Time Crystal

Article arXiv:1609.08684v1 [quant-ph] submitted to arXiv on 27 Sep 2016 by J. Zhang, P. W. Hess, A. Kyprianidis, P. Becker, A. Lee, J. Smith, G. Pagano, I.-D. Potirniche, A. C. Potter, A. Vishwanath, N. Y. Yao, C. Monroe

Spontaneous symmetry breaking is a fundamental concept in many areas of physics, ranging from cosmology and particle physics to condensed matter. A prime example is the breaking of spatial translation symmetry, which underlies the formation of crystals and the phase transition from liquid to solid. Analogous to crystals in space, the breaking of translation symmetry in time and the emergence of a “time crystal” was recently proposed, but later shown to be forbidden in thermal equilibrium. However, non-equilibrium Floquet systems subject to a periodic drive can exhibit persistent time-correlations at an emergent sub-harmonic frequency. This new phase of matter has been dubbed a “discrete time crystal” (DTC). Here, we present the first experimental observation of a discrete time crystal, in an interacting spin chain of trapped atomic ions. We apply a periodic Hamiltonian to the system under many-body localization (MBL) conditions, and observe a sub-harmonic temporal response that is robust to external perturbations. Such a time crystal opens the door for studying systems with long-range spatial-temporal correlations and novel phases of matter that emerge under intrinsically non-equilibrium conditions.

Commentary

Explanation by Jakub Zakrzewski, Marian Smoluchowski Institute of Physics, Jagiellonian University, 30-059 Krakow, Poland and published in October 15, 2012 in the journal Physics, 5, 116.

He writes that “researchers propose how to realize time crystals, structures whose lowest-energy states are periodic both in time and space…A time crystal has periodic structures both in space and time. Particles arranged in a periodic pattern in space rotate in one direction even at the lowest energy state, determining periodicity in time. (b) An experimental realization of a time crystal proposed by Li et al. uses ultracold ions confined in a ring-shaped trapping potential. The ions form a periodic structure in space and, under a weak magnetic field, they move along the ring, creating a time crystal.”

Report of Creation of first Quantum Time Crystals

Explanation  in AAAS website EurekAlert on 26 January 2017 of how scientists have actually created quantum time crystals.

Viewpoint Article in Physics.aps.org

18 January 2017, Phil Richerme, Physics Department, Indiana University reports on detailed theoretical recipes for making time crystals has been unveiled and swiftly implemented by two groups using vastly different experimental systems. He also provides useful references to original articles.

Confirmation of Existence of Time Crystals

Fiona Macdonald reports in Science Alert on 28 January 2017 that scientists have confirmed the existence of time crystals, a brand new form of matter.

“The discovery might sound pretty abstract, but it heralds in a whole new era in physics – for decades we’ve been studying matter that’s defined as being ‘in equilibrium’, such as metals and insulators. But it’s been predicted that there are many more strange types of matter out there in the Universe that aren’t in equilibrium that we haven’t even begun to look into, including time crystals. And now we know they’re real. The fact that we now have the first example of non-equilibrium matter could lead to breakthroughs in our understanding of the world around us, as well as new technology such as quantum computing.”