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




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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 on July 28 this year in the arXiv database, scientists are using Google (a quantum computer version of conventional computer bits) to create time crystals in the center of Google’s Sycamore quantum processor. About 100 seconds.

This strange new state, and the physical behavior it reveals, excites scientists so much that nine years ago humans timely predicted the existence of crystals.

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

This tendency towards disorder can explain many cases, e.g. For example, why the ingredients are easy to mix, but the mix is ​​difficult to separate or why the earphone cords are always rolled up in the pockets. This law also determines the direction of the arrow of time: the past universe will always be more ordered than the present universe. For example, if you turn the movie upside down, it will look 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 caught between two energy states above thermal equilibrium and shifts back and forth between those 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 bounce back and forth in the box they “get more and more confused and go through all sorts of arrangements” until the shaking stops. After opening the box, all the coins inside are randomly arranged, half up and half down. Regardless of how the coins are initially placed in the box, we can predict that at some point they will appear in this mess, half up and half down.

In the “box” of the Sycamore quantum processor from Google, we can now imagine the pound as a special currency. The quits can be 0 or 1 or can be the superposition of these two states as a coin is facing up or its back side. The strange thing about Time Crystals is that no matter how often they “tremble” between two states, the 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 eventually not appear as a random shape, but will get stuck between two states. It’s like remembering your initial state and then repeating this method. From this point of view, the time crystal is like a pendulum that never stops swinging.

“Even if you physically isolate a vibration from the entire universe, without friction and wind resistance, it will eventually stop vibrating. This is the result of the second law of thermodynamics. ”In 2015 he was one of the first scientists to discover the potential of this new substance, he emphasized. “Energy is initially concentrated in the center of mass of the pendulum, but at some point it will always change. This is the inner degree of freedom of matter like the oscillation of atoms in a pendulum wire. “

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

In the quantum world, objects have the dual properties of particles and waves. The wavelength in a certain area of ​​space indicates the probability of finding a particle in this space. However, the randomness (such as random defects in the crystal structure or the randomness of the contact strength between the beams) can lead to the particle waves canceling out 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 environment, ie the particle is localized.

Researchers use the process of particle localization on their experimental basis. They used 20 superconducting aluminum as quilts and then put them in one of two possible states. Next, these superconducting aluminum rods were bombarded with microwave rays and changed to a different state. The researchers repeated this process thousands of times, pausing the test at various times to record the Cupid’s position at that point in time. Overall, all of the quilts were transferred between the two structures and did not pick up any heat from the microwave beam – it was time for the crystal to be born.

They also noted the important clue that time crystals are the state of an object. When the environment changes, the position of the object is usually very stable. For example, if the ambient temperature changes slightly, the solid does not melt and the liquid does not suddenly evaporate or freeze. If the microwave beam that changed the position of the qubit changes slightly, if it changes slightly from the 180-degree “perfect rotation” the quid will also change to a different position.

“If you don’t get exactly 180 degrees, everything will be destroyed.” Pointed out Lazarites, “Even if you make a small mistake, time crystal becomes 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 anytime and anywhere. For example, if water is liquid, the flow of water molecules follows the same physical laws in every spatial position and in every direction. But when water is cooled and turned into ice, the molecules form a crystalline structure, and each molecule has its own specific position in the structure. In this case, all possible states are emptied, except where each water molecule chooses itself, and the spatial symmetry of the water is broken.

Just as water molecules become spatial crystals by breaking spatial asymmetry, time crystals are created by breaking time asymmetry. Before moving to the 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 symmetrical with the unique time shift). Next, the quid spun back and forth twice as long as the microwave beam. As a result, the unique time shift imposed by the laser successfully broke the symmetry and became the first object we knew could do.

With these peculiarities, many new discoveries can be made in the physics of time crystals, and the Google Sycamore quantum processor becomes an excellent platform for further study. However, there is still room for improvement. Like all quantum systems, the quantum system of the couplings must be completely isolated from the environment in order to prevent the “decomposition” of quits, which ultimately interrupts the quantum localization effect and destroys the time crystal. Researchers are still looking for better methods of processor isolation to minimize the effects of quantum decoupling, but they cannot be eliminated completely.

Even so, this test is still the best way to examine time crystals in a short amount 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 at processing the crystal’s decay. A comprehensive study.

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

However, the greatest benefit of time crystals may have been discovered: it enables scientists to further explore the limits of quantum mechanics.

“With it you can not only study the objects that exist in nature, but also design them yourself in order to explore what quantum mechanics allows and what does not,” emphasized Lazarites. That is not to say that it cannot be anything less than anything in nature – we have to create something ourselves. “(Sheet)



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