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Scientists get the first picture of a time crystal


imageWith the latest breakthrough, the eerie vibrations of a new, pulsating form of matter have been filmed for the first time using a special microscope. It allows us to see this strange, phase form of matter, which is very different from the usual solids, liquids, gases and plasmas.

The picture was taken by Maximus, an ultra-powerful X-ray microscope at the Helmholtz Center in Berlin. It gives us an idea of the behavior of new time crystals, which were first experimentally created in the laboratory in 2016. The discovery promises "outstanding new breakthroughs in basic research," says material published by the German-Polish team in Physical Review Letters.

What is a time crystal
image One Experiment That Created the First Time Crystal In short, time crystals are objects that exhibit the properties of crystals in both space and time.

To understand their properties, you can first remove the fourth dimension, time, and consider an ordinary three-dimensional crystal. What it is? A collection of atoms arranged in a specific repeating, systematic sequence.

Let's say ice cubes. Before water crystallizes, the space it occupies is uniform. You can take a sample from the bottom, top, or somewhere in the middle of the glass, and get the same shapeless mass. Which is one way to show that space exhibits symmetry.

However, when water crystallizes, the atoms form rigid, predetermined structures. The space occupied by the crystal has become periodic, it has a certain algorithm. The crystal has broken spatial symmetry because it shows repeating patterns in some directions.

Just as the atomic lattices of ordinary crystals repeat regular patterns in space, crystals of time repeat regular patterns in time. In practice, this means that they demonstrate the so-called temporal periodicity, oscillating between one and another energy configuration, like a clock.

imageFrank Wilczek The hypothesis of the existence of temporary crystals in 2012 put forward Frank Wilczek, Nobel Prize Laureate in Physics. He presented matter, in which, with all the external stability, some energy vibrations occur. That is, it does not change in space, but in time. Wilczek said that such structures can exist if they receive energy for their oscillation from a fault in the symmetry of time. According to his calculations, atoms can form a constantly repeating lattice in time, returning to their original position after equal intervals, thereby breaking the temporal homogeneity (symmetry).

An ice cube is a rare occurrence in nature. It has low entropy and is prone to destruction. The same is with temporary crystals: it is impossible to find them in nature, at least on Earth. The very fact of their existence seemed extremely doubtful. The structures seemed too ephemeral and far from reality.

imageJust as physics allows the spontaneous formation of crystals, the periodicity of which breaks the symmetry (uniformity) of space, it must also allow the spontaneous formation of temporary crystals, the periodicity of which breaks the symmetry of time. According to Wilczek, this will manifest itself in the periodic oscillation of various thermodynamic processes.

Wilczek presented the system in its lowest possible energy state, actually frozen in space. Like a normal crystal, only completely isolated from spatial vibrations. Then its fluctuations in time can be detected.

The idea seemed rather strange - a new kind of matter, different from others in its behavior in the fourth dimension. But in September 2016, a group of scientists at the University of Maryland laboratory in College Park unexpectedly confirmed Wilczek's theory. They created the first time crystal. For this, a ring of ytterbium ions was used, cooled to almost absolute zero (0.0000000001 K). A violation of temporal symmetry was recorded in the structure.

imageImage of the experiment at the University of Maryland New matter did show unusual properties. When the time crystal was influenced with a certain period or frequency, it did not react at the same frequency, but modified it “for itself”. If the laser applied a pulse to a chain of ions (forming a crystal of time) every ten seconds, these ions reacted with a period of not ten, but twenty, thirty, forty seconds. Or another multiple of the original period.

You can imagine three children jumping over a rope. Andrey and Vanya unwind her, and Katya jumps. Every three seconds, the hands of the guys make a full circle and return to their original position. The rope goes around Katya, she needs to jump once. Time symmetry is established between the objects, the period of which is equal to three seconds.

Now, in order to represent the time crystal, this time symmetry must be broken. The system will respond on a different frequency. Andrei and Vanya's hands make several full turns, and the rope makes only one turn. That is, they twisted the rope four times, but Katya needs to jump over only once. Which is rather strange (although not as strange as quantum mechanics, the correctness of which is now not widely doubted).

Following a group from the University of Maryland, a successful experiment in creating time crystals spent their colleagues at Harvard. They used a completely different experimental setup with densely packed nitrogen vacancy centers in diamonds. And again - we managed to create temporary crystals, albeit on a nano-scale.

imageThe installation for creating a temporary crystal from Harvard The system here was more complex, there were more atoms in it, and it well demonstrated this unusual property of a temporary crystal: a response to interaction with an interval exceeding the interaction interval. The structure was irradiated with a laser at a T interval, and the material reacted at a 2T interval. This is an extremely strange property that is not found in conventional materials. You can imagine a jelly cube that only starts vibrating with the second click.

imageAt the same time, the new type of matter very clearly and structuredly passed from one configuration to another, like a clock. Therefore, scientists assume that eventually it will be possible to make devices for measuring time (atomic clocks) from time crystals. They are also thought to be used as a storage medium for memory, a "hard disk" in quantum computers. In fact, both teams, from the University of Maryland and from Harvard, had previously worked on quantum computers. Therefore, according to them, they managed to switch to temporary crystals so quickly. The systems use the same principles, are designed in a similar way, and seem to be made for each other.

Norman Yao, a physicist at the University of California, Berkeley, who in 2017 first published a diagram for creating and tracking temporary crystals, and also helped the Harvard team, says:
For the last half century, we have studied only time-equilibrium matter, as in metals and dielectrics. We are just now starting to explore a whole new world of non-equilibrium matter.
A slightly more detailed analysis of the properties and methods of obtaining temporary crystals can be found here - here (in English).
What now
image Research into the properties of temporary crystals continues. For scientists, this is a real storehouse of knowledge, there are much more questions than answers. Detailed research came out in February in Physical Review Letters ... The work was jointly carried out by scientists from the Max Planck Institute for Intelligent Systems, University. Adam Mickiewicz and the Polish Academy of Sciences.

The joint German-Polish team was able to create a much (several million times) larger time crystal than before. And at room temperature. They got a new type of matter by strong uniform microwave pumping maser micron-sized permalloy strips. Their crystal consists of magnons - quasiparticles associated with the spin of electrons in a magnetic material. One of the scientists, Nick Traeger, says that the easiest way to comprehend this concept is to imagine magnons as analogous to photons. In the same way that photons are the quantization of light, magnons are the quantization of a spin wave within a magnetic material.

imageIn their experiment, Nick Treger, Pavel Grushetsky and others placed a small strip of magnetic material on a microscopic antenna through which they sent RF current. This microwave field produced an oscillating magnetic field - a source of energy that stimulated magnons (spin wave quasiparticles) in the strip.

Magnetic waves moved along the strip to the left and right, periodically spontaneously forming into a repeating pattern in space and time. Unlike conventional standing waves, this pattern was formed even before two converging waves could meet and intersect. Conclusion: this pattern, a pattern that regularly disappears and reappears on its own, must be a quantum effect. Actually, we can observe it on the video released by scientists:

Nick Treger says ininterview , posted on the website of the Max Planck Institute for Intelligent Systems:
This is, of course, a little strange and confusing. But, in short, we induce magnons in a strip using an antenna over the structure. That is, everything you can see in this video is a periodic pattern (formed by magnons). It follows its own periodic motion in space-time, that is, it forms a time crystal.
Gisela Schütz, Director of the Institute for Intelligent Systems. Max Planck, head of the department of modern magnetic systems, in the article notes the uniqueness of the Maximus X-ray camera, which was able to capture this picture:
Not only can it see wave fronts with a very high resolution, 20 times sharper than the best light microscope. It can do this at up to 40 billion frames per second and is extremely sensitive to magnetic phenomena.
imagePavel Grushetsky, a scientist from the Faculty of Physics at Adam Mickiewicz University in Poznan, says:
We were able to show that space-time crystals are much more stable and widespread than previously thought. Our magnon crystal forms at room temperature! And particles can interact with it - in contrast to an isolated system created at absolute zero. Moreover, it has reached a size that could be used. Such an experiment opens up a host of potential useful applications for this new kind of matter.
Joachim Graefe, the last author of the publication in Physical Review Letters, concludes:
Classic crystals, as we know, have a very wide range of applications. Now we see that there are crystals that can manifest their properties not only in space, but also in time. This adds another dimension to the possible use cases.

It seems clear to me that time crystals will be useful wherever very efficient devices are needed for frequency shift keying or accurate sampling. The potential for communications technology, radar or quantum machines is enormous.

Our colleagues are also delighted with how these structures can be used to study the physics of nonlinear waves. But first, now we want to get a more fundamental understanding of the temporal vibrations of crystals of space-time. And only after that we will think about how it can be used in practice.
Skull 10 march 2021, 16:04
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