Strange “time crystals” created on quantum computers can change physics forever-scientific study-cnBeta.COM

September 17, Beijing Time News, according to foreign media reports,Researchers have recently developed a new time-time crystal using quantum computers.Time crystals can always rotate between two states without losing any energy, so they have successfully avoided one of the most important definitions of physics — the second law of thermodynamics. The law states that the disorder of the isolated system (i.e. “entropy”) must always be increasing. And this magical time crystal will always be stable.


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These time crystals are generated on Google’s Sycamore chip and stored in a quantum cryostat.

According to a study published in the database arXiv on July 28 this year, scientists use Google (a quantum computer version of traditional computer bits) to create time crystals at the center of Google’s Sycamore quantum processor. About 100 seconds.

This strange new condition and the physical behavior it reveals excites scientists so much that nine years ago, people predicted the existence of crystals in time.

From the point of view of physicists, time crystals are a very magical object because they are not governed by the second law of thermodynamics, one of the most unbreakable laws of physics. The law states that entropy is always increasing. If you want to improve order, you need to increase energy.

This tendency to disorder can explain many cases, such as why the ingredients are easy to mix but the mixture is difficult to separate, or the earphone cords in your pockets are always curled together. This law also determines the direction of the time arrow: the past universe will always be more orderly than the present universe. For example, if you turn the film upside down, it looks different because the flow of this entropy goes against your intuition.

But time crystals do not follow this law. It does not gradually reach thermal equilibrium (i.e., energy or temperature is evenly distributed around it), but is trapped between two energy states above the thermal equilibrium and shifts back and forth between these two states.

To illustrate how unusual this phenomenon is, let’s take an example: Suppose a closed box is filled with coins and then shaken a million times. As these coins jump back and forth in the box, they “become more and more confused and pass all possible arrangements” until the shake stops. After opening the box, all the coins inside are arranged randomly, half up and half down. No matter how the coins in the box are initially placed, we can predict that they will eventually appear in this disorder, half upper and half lower.

In the “box” of Google’s Sycamore quantum processor, we can now think of the quid as a particular currency. The quits may be 0 or 1, or may be the super position of these two states, as one coin faces or its back is above. The strange thing about time crystals is that no matter how many times they “shake” between two states, the quits of time crystals cannot be converted to a very low energy level (equivalent to the random arrangement of coins). Go from the starting position to the second level and then jump again.

The time crystal will not eventually appear as a random shape, but will be stuck between two states. It is like remembering its initial state and then repeating this method. From this point of view, the time crystal is like a pendulum that does not stop swinging.

“Even if you physically isolate an oscillation from the entire universe with zero friction and wind resistance, it will eventually stop oscillating. This is the result of the second law of thermodynamics.” He was one of the first scientists to discover the potential of this new substance in 2015, he pointed out. “Energy is initially concentrated at the center of mass of the pendulum, but it will always change eventually. This is the internal degree of freedom of matter like the vibration of atoms inside a pendulum wire.”

In fact, large-scale objects cannot be like time crystals, because only the ruling law of microscopic world-quantum mechanics can make time crystals.

In the quantum world, objects have the dual properties of particles and waves. The wavelength in a given area of ​​space indicates the probability of finding a particle in that space. However, the randomness (such as random defects in the crystal structure or the randomness of the contact strength between quits) may cause the particle waves to cancel each other at a distance other than a small fraction. In this way, the position of the particle is adjusted so that it cannot move or change its position or achieve thermal equilibrium with the surrounding environment, i.e. the particle is localized.

Researchers use the process of localization of particles on their experimental basis. They used 20 superconducting aluminum as quilts and then set each of them into one of two possible states. Next, these superconducting aluminum rods were bombarded with microwave beams and transferred to another state. The researchers repeated this process thousands of times, and paused the test at different times to record the position of the cupid at that time. Overall all the quilts were transferred between the two structures and did not absorb any heat from the microwave beam – it was time for the crystal to be born.

They also noted the important indication that time crystals are the state of an object. When the surrounding environment changes, the position of the object is usually very stable. For example, if the ambient temperature changes slightly, the solid will not melt, and the liquid will not suddenly evaporate or freeze. In the same way, if the microwave beam used to change the position of the qubit changes slightly, the quid will change to another position if it changes slightly from the 180 degree “perfect flip”.

“If you don’t reach exactly 180 degrees, everything will be destroyed.” Lazarites pointed out, “Even if you make a small mistake, Time Crystal will turn into magic.”

Breaking the symmetry of physics is another sign of a change in the position of matter. Physical symmetry means that the laws of physics are the same for the same object at any time or place. For example, when water is liquid, the flow of water molecules in every spatial position and in every direction follows the same laws of physics. But if water is cooled and turned into ice, the molecules will form a crystalline structure, and each molecule will have its own specific position in the structure. In this case, all possible states are emptied, except for the place where each water molecule selects itself, and the spatial symmetry of the water is broken.

Just as water molecules become spatial crystals by breaking the asymmetry of space, so time crystals are formed by breaking the asymmetry of time. Before they switch to Time Crystal position, each row of qubits is always symmetrical. But the rotation of the microwave beam divides the static position of these quits into separate sections (the symmetry used by the laser becomes symmetric with the unique time translation). Next, the quid turned back and forth over a period of twice as long as the microwave beam. As a result, the unique time translation imposed by the laser successfully broke the symmetry and became the first object we knew could do this.

With these peculiarities, many new discoveries in physics can be made around time crystals, and the Google Sycamore quantum processor will become an excellent platform for further study. However, it still has room for improvement. Like all quantum systems, the quantum system of couplings must be completely isolated from the environment to prevent the “decomposition” of quits, which will eventually disrupt the quantum localization effect and destroy the time crystal. Researchers are still looking for better processor isolation methods to minimize the impact of quantum decoupling, but they cannot be completely eliminated.

Nevertheless, this test is still the best way to study time crystals in a short period of time. Although many projects have successfully developed materials such as time crystals (using diamonds, helium-3 superfluids, a half-particle called “magnon” and the Bose-Einstein capacitor), they are much faster to process the crystal’s decay. A comprehensive study.

These crystals are very innovative in theory, good and bad, because physicists are not yet clear about their usefulness. But von Kessellink proposed that they could be used on high-precision sensors. Others have suggested that these crystals could be used to improve memory or to build quantum computers at faster processing speeds.

However, the greatest use of time crystals may have been revealed: allowing scientists to further explore the boundaries of quantum mechanics.

“It not only allows you to study the objects that exist in nature, but also allows you to design it yourself, allowing you to explore what quantum mechanics allows you to do and what you are not allowed to do,” Lazarites pointed out. That doesn’t mean it can’t be less than anything in nature — we have to create something ourselves. “(Leaf)

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