Constantly on the move without consuming energy
For several months, there has been talk that researchers have managed to create time crystals - strange crystals whose atomic structure repeats not only in space, but also in time, which means that they are constantly moving without the expenditure of energy.
Now it has been officially confirmed: Researchers have only recently revealed in detail how to create and measure these strange crystals. And two independent groups of scientists claim that they actually managed to create time crystals in the laboratory, using the instructions provided, thereby confirming the existence of a completely new type of matter.
The discovery may seem completely abstract, but it heralds the beginning of a new era in physics, because for many decades we have studied only matter, which, by definition, was 'in equilibrium': metals and insulators.
But there were suggestions about the existence in the Universe of a variety of strange types of matter that are not in equilibrium and which we have not even begun to study, including time crystals. We now know that this is not fiction.
The very fact that we now have the first example of 'non-equilibrium' matter could lead to a breakthrough in our understanding of the world around us, as well as technologies such as quantum computing.
“This is a new kind of matter, period. But it's also cool that this is one of the first instances of 'non-equilibrium' matter,”says lead researcher Norman Yao of the University of California, Berkeley.
“For the entire second half of the last century, we have been studying matter in equilibrium, such as metals and insulators. And only now we have stepped into the territory of 'non-equilibrium' matter."
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But let's pause and look back, the concept of time crystals has been around for several years.
They were first predicted by Nobel laureate physics theorist Frank Wilczek in 2012. Time crystals are structures that appear to be in motion even at the slightest level of energy known as the ground state or state of rest.
Usually, if matter is in the ground state, also known as the state of zero energy of the system, it means that motion is theoretically impossible, because it requires energy.
But Wilczek argued that this does not apply to the crystals of time.
In ordinary crystals, the atomic lattice is repeated in space, just like the carbon lattice of diamond. But, like a ruby or an emerald, they do not move because they are in equilibrium in their basic state.
And in time crystals, the structure is also repeated in time, not only in space. And therefore they are in motion in the basic state.
Imagine jelly. If you poke it with your finger, it will begin to vibrate. The same thing happens in crystals of time, but the big difference is that they do not require energy to move.
A time crystal is like a constantly vibrating jelly in its usual, basic state, and this is what makes it a new type of matter - 'nonequilibrium' matter. Which just can't sit still.
But it is one thing to predict the existence of such crystals, and quite another to actually create them, which is what happened in the latest research.
Yao and his team created a detailed diagram in which they described in detail how to create and measure the characteristics of a time crystal, and even predict what the various phases surrounding a time crystal should be, in other words, they described the equivalents of solid, liquid and gaseous states of a new type of matter.
Yao called the article published in Physical Review Letters "a bridge between theoretical idea and experimental implementation."
And this is not speculation at all. Following Yao's instructions, two independent groups - one from the University of Maryland and the other from Harvard - managed to create their own time crystals.
The results of both studies were announced late last year on arXiv.org (here and here), and were sent to peer-reviewed journals for publication. Yao co-authored both articles.
While we wait for publications, it is worth remaining skeptical about the statements. But the very fact that two independent groups managed to create time crystals using the same scheme in completely different conditions sounds promising.
At the University of Maryland, time crystals were created from a chain of 10 ytterbium ions, all with entangled electron spins.
The key to turning this base into a crystal of time was to keep the ions in disequilibrium, and to do this, they were hit in turn from two lasers. One laser created a magnetic field, the second laser partially unrolled the spins of the atoms.
Since the spins of the atoms were initially entangled, they soon entered the stable, repetitive spin-rotation pattern that defines the crystal.
This was normal, but in order to become a crystal of time, the system had to break the symmetry in time. While observing the chain of ytterbium atoms, the researchers noticed something unusual.
Two lasers periodically striking the ytterbium atoms caused a repetition in the system with a period twice as long as the period of the 'shocks', which was exactly what could not occur in a normal system.
“Wouldn't it be very strange if you poked jelly and found that it reacts to it with different time periods?” - explains Yao.
“But this is the nature of the time crystal. You have some kind of pathogen with a period of T, but the system is somehow synchronized, and you observe its movement with a period exceeding T."
Depending on the magnetic field and the pulsation of the laser, the time crystal could then change its phase, like a melting cube.
Crystal from Harvard was different. The researchers created it using dense nitrogen vacancy centers in the diamond, but they came up with the same result.
“These similar results from two very different systems confirm that time crystals are a widespread form of matter, and not some curious feature that is only observed in a small, special system,” explains Phil Rifermey of Indiana University in a related study. work note, he did not participate in the study, but reviewed the article.
"The observation of this single crystal of time … confirms that symmetry breaking can occur in all areas of nature, and this opens up new areas for research."
Yao's diagram was published in Physical Review Letters, and you can read a Harvard paper on time crystals here, and a University of Maryland paper here.