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article imageEssential Science: Physicists detect a 'time' crystal

By Tim Sandle     May 7, 2018 in Science
Scientists have uncovered hints of a time crystal. This is a a crystalline form of matter that 'ticks' when exposed to an electromagnetic pulse. The location of the discovery is almost as unusual as the discovery itself.
The implications of the discovery of the time crystal mean that physicists now new puzzles to solve, relating to how time crystals form in the first place. Once this is pinned down, the potential applications could be considerable for computing and other devices reliant upon time measurements, such as atomic clocks, gyroscopes, and magnetometers. What has got some scientists interested is that time crystals could form the basis for a nearly perfect memory unit for powerful quantum computers.
Crystals
Time crystals were first theorized in 2016. They differ from ordinary crystals. A conventional crystal, something like salt (sodium chloride) or quartz, is a three-dimensional construct of ordered spatial crystals. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. Quartz is a mineral composed of silicon and oxygen atoms; it is a trigonal crystal, which is a six-sided prism terminating with six-sided pyramids at each end.
Quartz crystal cluster from Tibet
Quartz crystal cluster from Tibet
JJ Harrison
Within the crystal structure, atoms are arranged in a repeating system. The crystal lattice extends in all directions. The method for determining crystal structures is is X-ray diffraction, and the outputs are stored in crystallographic databases.
Time crystals
A time crystal is a structure that repeats in time, as well as in space. An ordinary three-dimensional crystal, of the type described above, have a repeating pattern in space; however, they remain unchanged as time passes. Time crystals repeat themselves in time as well as structure. This means the crystal changes from moment to moment. This phenomenon arises because a time crystal never reaches thermal equilibrium.
To the casual observer time crystals look like ordinary crystals. However, through specialized equipment scientists can see that their atoms are actually oscillating: spinning first in one direction, and then the other. The oscillations are referred to as time crystal "ticking", and these atomic spins are locked to a very regular frequency.
First time crystal
Time crystals were theorized in 2012. Then, in 2016, a paper was published describing the discovery of a crystal with special properties ("Discrete Time Crystals: Rigidity, Criticality, and Realizations"). This was followed by Harvard physicists creating a time crystal from a nitrogen-vacancy diamond. This was achieved two different mediums: lasers and trapped ions.
Apart from these events, no further time crystals had been detected - until now.
New discovery
With the new discovery, Yale scientists have created a time crystal in a solid material called monoammonium phosphate, the researchers report in both Physical Review Letters ("Observation of Discrete-Time-Crystal Signatures in an Ordered Dipolar Many-Body System") and Physical Review B ("P31 NMR study of discrete time-crystalline signatures in an ordered crystal of ammonium dihydrogen phosphate").
The monoammonium phosphate time crystal was created in a solid material with an orderly physical structure: a traditional crystal. What's usual about this crystal, Science News reports, is that it is commonly used in crystal growing kits aimed at youngsters and it crystallizes in tetragonal prisms. In industry, monoammonium phosphate is often used in the blending of dry agricultural fertilizers.
The researchers used nuclear magnetic resonance to look for a discrete time crystal signature. According to lead researcher Professor Sean Barrett: "Our crystal measurements looked quite striking right off the bat." "Our work suggests that the signature of a discrete time crystal could be found, in principle, by looking in a children's crystal growing kit."
Following the latest discovery, the U.S. Department of Defense has announced a program to fund more research into time crystal systems.
Essential Science
A strikingly beautiful image of the tadpole galaxy.
A strikingly beautiful image of the tadpole galaxy.
Unknown
This article is part of Digital Journal's regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week's focus was on how artificial intelligence is bringing new tools to astronomy, in terms of machine intelligence being deployed to detect and recognizes interstellar objects. The most sophisticated form is a 'face recognition' for galaxies.
The week before was about the U.S. Great Lakes and human drug waste. Research has uncovered levels of antidepressants not only in the water but also in the brains of fish. This signals the polluting effect of wastewater and sewage treatment facilities.
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