domeet webmaster

This article is from WeChat official account:Principle (ID: principle1687), author: Stefan Forstner (post-doctoral researcher at the University of Queensland), head Figure from: “ant-man” stills

one

Have you ever been in multiple places at the same time? If your size is much larger than an atom, the answer must be no. But particles are different, they are governed by the laws of quantum mechanics. According to quantum mechanics, several different possible situations can coexist simultaneously.

Quantum systems are controlled by wave functions, which are mathematical objects that describe the probabilities of these different possible situations. The coexistence of these different possibilities in the wave function is called the superposition of different states. For example, when a particle exists in several different places at the same time, we call it spatial superposition. Only when the measurement is performed, the wave function will collapse, making the system finally in a certain state.

Generally speaking, quantum mechanics applies to the world of microscopic particles at the atomic level. What it means for large-scale objects is still inconclusive. In a study recently published in “Optical Design”, researchers put forward an experiment that is expected to completely solve this thorny problem.

two

In the 1930s, the Austrian physicist Erwin Schrödinger (Erwin Schrödinger) proposed a famous thinking experiment-the box A cat in the house. According to the theory of quantum mechanics, Schrödinger’s cat can be both alive and dead.

In Schrödinger’s thought experiment, a cat was placed in a sealed box. In this box, there was a random quantum event with a half chance of killing the cat. The cat in the box is both dead and alive until the box is opened and observed. In other words, before being observed, cats existed in the form of (multiple possibilities) wave functions. When it is observed, it becomes a certain object.

After many arguments, the scientific community at that time reached a consensus on the Copenhagen interpretation. What this basically says is that quantum mechanics can only be applied to atomic and molecular scales, and cannot describe larger objects.

But in the past two decades, physicists have created quantum states in objects that are large enough to be visible to the naked eye and composed of trillions of atoms. However, spatial superposition has not been included in the list for a long time.

three

But how does the wave function become a “real” object? This is what physicists call the “quantum measurement problem.” For nearly a century, it has troubled scientists and even philosophers.

If there is a mechanism that can eliminate the possibility of quantum superposition of large-scale objects, then the wave function will be “disturbed” in some way, thereby generating heat. If this kind of heat can be found, it means that large-scale quantum superposition is impossible. If this heat can be eliminated, it means that nature may not mind “quantization” on any scale. If it is the latter, as technology advances, we should be able to put large objects, even sentient beings, in a quantum state.

Schematic diagram of the resonator in quantum superposition. The red wave represents the wave function. | Image source: Christopher Baker

Physicists didn’t know that it prevented large-scaleWhat is the mechanism of quantum superposition? Some scientists said that this may be an unknown field of cosmology, while others suspect that gravity may have something to do with it. This year’s Nobel Laureate in Physics Roger Penrose (Roger Penrose) once thought that biological consciousness may be inseparable from this.

four

For the past decade or so, physicists have been eagerly searching for traces of heat that indicate that the wave function is disturbed. To find this kind of heat, people need a way to (as completely as possible) to suppress all other excess heat sources, because those heat sources may hinder Accurate measurement. Scientists also need to control an effect called quantum “reaction”, which is the heat generated by observing the action itself.

In this new study, the researchers designed an experiment that is expected to reveal the possibility of space superimposed on large-scale objects. None of the best experiments to date have achieved this goal.

Like the previous experiment, the newly designed experiment will need a cooler that is cooled to only 0.01 Kelvin higher than absolute zero, but it will use a higher frequency resonator, so it can Eliminate the heat problem of the refrigerator itself.

Under this combination of extremely low temperature and extremely high frequency, the vibration in the resonator will undergo a Bose condensation process. You can simply think of it as the resonator being frozen so hard that the heat in the refrigerator can’t control it at all. The newly designed experiment will also use a different measurement strategy. It does not pay attention to the movement of the resonator, but to see how much energy it has. This method can also suppress the reaction heat well.

So how will the experiment be conducted? The researchers plan to let a single photon enter the resonator and bounce back and forth millions of times, absorbing all the remaining energy. These particles will eventually leave the resonator and take away excess energy. By measuring the energy of the photons, the researchers can determine whether there is heat in the resonator.

If there is heat, it means that the wave function has been affected by some (out of the researcher’s control)Know the source of interference. This means that large-scale superposition is impossible.

Five

The experiment proposed by the new research is extremely challenging. In the words of the author of the paper, “This is not the kind of thing you can arrange on Sunday afternoon.” It may require years of development, millions of dollars in funding, and a group of experienced experimental physicists.

Nevertheless, it can answer one of the most interesting questions about our reality: Is everything quantum?

The original title is “Could Schrödinger’s cat exist in real life? Our research may soon provide the answer”, first published in The Conversation on October 14, 2020 .

Original link: https://theconversation.com/could-schrodingers-cat-exist-in-real-life-our-research-may-soon-provide-the- answer-147752, the article is translated based on the CC agreement, and the Chinese content has been slightly edited for reference only. All content is subject to the original text.

This article is from WeChat official account:Principle (ID: principalia1687) author: Stefan Forstner (postdoctoral researcher at the University of Queensland)