Schrödinger's theory in simple terms. Schrödinger's cat: is he alive or not? The essence of the experiment

As Heisenberg explained to us, because of the principle of uncertainty, the description of objects in the quantum microcosm is of a different nature than the usual description of objects in the Newtonian macrocosm. Instead of spatial coordinates and velocities, which we are used to describing mechanical motion, for example, a ball on a billiard table, in quantum mechanics, objects are described by the so-called wave function. The “wave” crest corresponds to the maximum probability of finding a particle in space at the time of measurement. The motion of such a wave is described by the Schrödinger equation, which tells us how the state of a quantum system changes over time.

Now about the cat. Everyone knows that cats love to hide in boxes (). Erwin Schrödinger was also aware. Moreover, with purely Nordic fanaticism, he used this feature in a famous thought experiment. Its essence was that a cat was locked in a box with a hellish machine. The machine is connected via a relay to a quantum system, for example, a radioactively decaying substance. The probability of decay is known and amounts to 50%. The infernal machine is triggered when the quantum state of the system changes (decay occurs) and the cat dies completely. If we give the system "Cat-box-hellish machine-quanta" to itself for one hour and remember that the state of a quantum system is described in terms of probability, then it becomes clear that it will probably not work to find out whether the cat is alive or not at a given time. just as it will not work out to accurately predict the fall of a coin heads or tails in advance. The paradox is very simple: the wave function describing a quantum system mixes in itself two states of a cat - it is alive and dead at the same time, just as a bound electron with equal probability can be located anywhere in space equidistant from an atomic nucleus. If we don't open the box, we don't know exactly how the cat is there. Without making observations (read measurements) over an atomic nucleus, we can describe its state only by a superposition (mixing) of two states: a decayed and non-decayed nucleus. A nuclear-dependent cat is both alive and dead at the same time. The question is: when does the system cease to exist as a mixture of two states and choose one specific one?

The Copenhagen interpretation of the experiment tells us that the system ceases to be a mixture of states and chooses one of them at the moment when an observation occurs, it is also a measurement (the box opens). That is, the very fact of measurement changes physical reality, leading to the collapse of the wave function (the cat either becomes dead or remains alive, but ceases to be a mixture of both)! Think about it, the experiment and the measurements accompanying it change the reality around us. For me personally, this fact is taken out by the brain much stronger than alcohol. The notorious Steve Hawking also takes this paradox hard, repeating that when he hears about Schrödinger's cat, his hand reaches for the Browning. The acuteness of the reaction of the outstanding theoretical physicist is due to the fact that, in his opinion, the role of the observer in the collapse of the wave function (dumping it to one of two probabilistic states) is greatly exaggerated.

Of course, when Professor Erwin in the distant 1935 conceived his cat-mockery, it was a witty way to show imperfection quantum mechanics... Indeed, a cat cannot be alive and dead at the same time. As a result of one of the interpretations of the experiment, the contradiction between the laws of the macro-world (for example, the second law of thermodynamics - the cat is either alive or dead) and the micro-world (the cat is alive and dead at the same time) became obvious.

The above is applied in practice: in quantum computing and in quantum cryptography. A light signal is transmitted over a fiber-optic cable, which is in a superposition of two states. If the attackers connect to the cable somewhere in the middle and tap off the signal there in order to eavesdrop on the transmitted information, this will collapse the wave function (from the point of view of the Copenhagen interpretation, an observation will be made) and the light will go into one of the states. By conducting statistical tests of the light at the receiving end of the cable, it will be possible to detect whether the light is in a superposition of states or has already been observed and transmitted to another point over it. This makes it possible to create communication means that exclude invisible signal interception and eavesdropping.

Another most recent interpretation of Schrödinger's thought experiment is the story of Sheldon Cooper, the hero of the TV series Theory big bang"(" Big Bang Theory "), which he recited for Penny's less educated roommate. The essence of Sheldon's story is that the concept of Schrödinger's cat can be applied in relationships between people. In order to understand what is happening between a man and a woman, what kind of relationship between them: good or bad, you just need to open the box. Before that, the relationship is both good and bad.

Welcome to the blog!

If you are interested in an article on a topic from quantum physics then chances are good that you love The Big Bang Theory. So, Sheldon Cooper came up with a fresh interpretation Schrödinger's thought experiment(you can find a video with this fragment at the end of the article). But in order to understand the dialogue between Sheldon and his neighbor Penny, let us first turn to the classical interpretation. So Schrödinger's Cat in simple words.

In this article, we'll cover:

A short historical background
Description of the experiment with Schrödinger's Cat
The answer to Schrödinger's cat paradox
Sheldon's interpretation of Schrödinger's Cat paradox

Good news right away. During the experiment Schrödinger's cat was not injured... Because the physicist Erwin Schrödinger, one of the founders of quantum mechanics, conducted only a thought experiment.

A short historical background

Before diving into the description of the experiment, let's make a mini excursion into history.

At the beginning of the last century, scientists managed to look into the microcosm. Despite the external similarity of the "atom-electron" model with the "Sun-Earth" model, it turned out that the familiar Newtonian laws of classical physics do not work in the microworld. Therefore, there appeared new science- quantum physics and its component - quantum mechanics. All microscopic objects of the microworld were called quanta.

Attention! One of the postulates of quantum mechanics is "superposition". It will be useful for us to understand the essence of Schrödinger's experiment.

"Superposition" is the ability of a quantum (it can be an electron, a photon, the nucleus of an atom) is not in one, but in several states at the same time or is in several points of space at the same time, if no one is watching him

It is difficult for us to understand this, because in our world an object can have only one state, for example, be, either alive or dead. And it can only be in one specific place in space. You can read about "superposition" and the stunning results of quantum physics experiments in this article.

Here is a simple illustration of the difference between the behavior of micro and macro objects. Place a ball in one of the 2 boxes. Because the ball is an object of our macro world, you can say with confidence: "The ball lies only in one of the boxes, while the second is empty." If instead of a ball you take an electron, then the statement will be true that it is simultaneously in 2 boxes. This is how the laws of the microworld work. Example: the electron in reality does not revolve around the nucleus of the atom, but is located at all points of the sphere around the nucleus at the same time. In physics and chemistry, this phenomenon is called the "electron cloud".

Summary. We realized that the behavior of a very small object and large object obey different laws. The laws of quantum physics and the laws of classical physics, respectively.

But there is no science that would describe the transition from the macrocosm to the microcosm. So, Erwin Schrödinger described his thought experiment just in order to demonstrate the incompleteness general theory physics. He wanted Schrödinger's paradox to show that there is a science for describing large objects ( classical physics) and science for describing micro-objects (quantum physics). But there is not enough science to describe the transition from quantum systems to macrosystems.

Description of the experiment with Schrödinger's Cat

Erwin Schrödinger described a thought experiment with a cat in 1935. The original version of the description of the experiment is presented in Wikipedia ( Schrödinger's cat Wikipedia).

Here is a version of the description of the experiment Schrödinger's Cat in simple terms:

A cat was placed in a closed steel box.
In the "Schrödinger's box" there is a device with a radioactive nucleus and poisonous gas placed in a container.
The nucleus can decay within 1 hour or not. The probability of decay is 50%.
If the nucleus decays, then the Geiger counter will record this. The relay will work and the hammer will break the container with gas. Schrödinger's cat will die.
If not, then Schrödinger's cat will live.

According to the law of "superposition" of quantum mechanics, at a time when we are not observing the system, the nucleus of an atom (and hence the cat) is in 2 states simultaneously. The nucleus is in a disintegrated / non-disintegrated state. And the cat is alive / dead at the same time.

But we know for sure that if the "Schrödinger box" is opened, then the cat can only be in one of the states:

if the core has not decayed, our cat is alive
if the core disintegrated - the cat is dead

The paradox of the experiment is that according to quantum physics: before opening the box, the cat is both alive and dead at the same time, but according to the laws of physics of our world, this is impossible. cat may be in one specific state - to be alive or to be dead... There is no mixed state of "cat alive / dead" at the same time.

Before getting a clue, watch this wonderful video illustration of the paradox of the experiment with Schrödinger's cat (less than 2 minutes):

Solution to Schrödinger's Cat Paradox - Copenhagen Interpretation

Now the answer. Pay attention to the special riddle of quantum mechanics - observer paradox... The object of the microworld (in our case, the core) is in several states at the same time just until we are watching the system.

For example, the famous experiment with 2 slits and an observer. When the electron beam was directed onto an opaque plate with 2 vertical slits, then on the screen behind the plate the electrons painted a "wave pattern" - vertical alternating dark and light stripes. But when the experimenters wanted to “see” how the electrons fly through the slits and set the “observer” from the side of the screen, the electrons painted not a “wave pattern” on the screen, but 2 vertical stripes. Those. behaved not like waves, but like particles.

It seems that quantum particles decide for themselves what state they assume at the moment when they are "measured".

Based on this, the modern Copenhagen explanation (interpretation) of the phenomenon of "Schrödinger's Cat" sounds like this:

As long as no one is watching the "cat-core" system, the core is in a decayed / non-decayed state at the same time. But it is wrong to say that the cat is alive / dead at the same time. Why? Because quantum phenomena are not observed in macrosystems. It would be more correct to speak not about the "cat-core" system, but about the "core-detector (Geiger counter)" system.

The nucleus chooses one of the states (decayed / non-decayed) at the time of observation (or measurement). But this choice does not occur at the moment when the experimenter opens the box (the opening of the box takes place in the macrocosm, very far from the world of the nucleus). The kernel chooses its state at the moment it enters the detector. The point is that the system has not been adequately described in the experiment.

Thus, the Copenhagen interpretation of the Schrödinger's Cat paradox denies that before the opening of the box, Schrödinger's Cat was in a state of superposition - it was in the state of a living / dead cat at the same time. A cat in the macrocosm can and is in only one state.

Summary. Schrödinger did not fully describe the experiment. It is not correct (more precisely, it is impossible to connect) macroscopic and quantum systems. Quantum laws do not apply in our macrosystems. In this experiment, it is not the "cat-core" that interact, but the "cat-detector-core". The cat is from the macrocosm, and the "detector-core" system is from the microcosm. And only in its quantum world, the nucleus can be in 2 states at the same time. This occurs until the moment of measurement or interaction of the nucleus with the detector. A cat in its macrocosm can and is only in one state. That's why, it is only at first glance that it seems that the state of the cat "alive and dead" is determined at the moment the box is opened. In fact, its fate is determined at the moment the detector interacts with the nucleus.

The final summary. The state of the "detector-core-cat" system is connected NOT with the person - the observer of the box, but with the detector - the observer of the nucleus.

Fuh. My brains almost boiled! But how pleasant it is to understand the answer to the paradox! As in an old student joke about a teacher: "While I was talking, I understood it myself!"

Sheldon's interpretation of Schrödinger's Cat paradox

Now you can relax and listen to the most recent interpretation of Schrödinger's thought experiment from Sheldon. The essence of his interpretation is that it can be applied in relations between people. To understand good relationship between a man and a woman or bad - you need to open the box (go on a date). And before that, they are both good and bad at the same time.

Well, how do you like this "cute experiment"? In our time, Schrödinger would have fallen from animal advocates for such atrocious thought experiments with a cat. Or maybe it was not a cat, but Schrödinger's Cat ?! Poor girl, has suffered from this Schrödinger (((

See you in the next publications!

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- a thought experiment of the physicist Erwin Schrödinger, the essence of which is that the cat in the box is alive and dead at the same time. Thus, the scientist proved the incompleteness of quantum mechanics in the transition from subatomic systems to macroscopic ones.

Origin

The Austrian theoretical physicist Erwin Schrödinger in 1935, in his article Die gegenwärtige Situation in der Quantenmechanik (Die gegenwärtige Situation in der Quantenmechanik) in Naturwissenschaften, proposed an experiment with a cat in a box.

We take the cat and place it in the box. The box contains an atomic nucleus and a container with a poisonous gas. The probability of nuclear decay is 50%, if it takes place, the container with gas will open and the cat will die. If decay does not occur, the cat is alive. According to the basics of quantum mechanics, before we open the box, the cat is in a state of quantum superposition - that is, in all states at the same time.

It turns out that in the "cat-core" system, a cat can be alive or dead with the same probability of 50%. Or he is both alive and dead at the same time.

Popularity on the Internet

For the first time on the Internet, the issue with Schrödinger's cat was discussed in May 1990 on the Usenet's sci.physics forum. On August 9, 2000, a poem dedicated to Schrödinger's cat was published on the Straight Dope Q&A forum.

In August 2004, online store ThinkGeek began selling T-shirts that read “Schrödinger's cat is dead”.

On January 4, 2006, the Schrödinger comic was released in the Xkcd comic series.

”- The last panel of this comic is funny and unfunny at the same time. Until you read it, you cannot tell how it will end up.

- Heck"

On June 2, 2007, the I Can Has Cheezburger website published a picture of a cat in a box with the caption: "In your quantum box ... one cat ... maybe."

The culmination of the popularity of Schrödinger's cat was the Google Doodle dedicated to him, which appeared on August 12, 2013 - on the day of Erwin Schrödinger's 126th birthday.

Popular culture references

Films, TV series, books and computer games, where this experiment was mentioned, played a significant role in the popularization of Schrödinger's cat in popular culture. Here are just a few examples.

In episode 16 of the sixth season of "Futurama," the police arrest Schrödinger and his cat.

In the second episode of the first season, Rick and Morty, the protagonists meet with Schrödinger's cats in a parallel reality.

Sheldon Cooper, in The Big Bang Theory, used Schrödinger's cat theory to explain to Penny how relationships between men and women work.

Meaning

Schrödinger's cat is not only an Internet meme, but also a hero of popular culture. A cat that is both alive and dead at the same time symbolizes a kind of ambiguity. Schrödinger is remembered when something is both funny and not, or when something is both prohibited and permitted. For example, a traffic light with a red and green signal at the same time is Schrödinger's traffic light.

Gallery

Yuri Gordeev
Programmer, game developer, designer, artist

Schrödinger's Cat is a thought experiment proposed by one of the pioneers of quantum physics to show how strange quantum effects look when applied to macroscopic systems.

I will try to explain in really simple words: gentlemen of physics, do not exact. The phrase "roughly speaking" is implied below before each sentence.

On a very, very small scale, the world is made up of things that behave in very unusual ways. One of the strangest characteristics of such objects is the ability to be in two mutually exclusive states at the same time.

What is even more unusual from an intuitive point of view (someone will even say, creepy) - the act of purposeful observation eliminates this uncertainty, and an object that has just been in two contradictory states at the same time appears before the observer in only one of them, like nothing never happened, looks to the side and whistles innocently.

At the subatomic level, everyone has long been accustomed to these antics. There is a mathematical apparatus that describes these processes, and knowledge about them has found a variety of applications: for example, in computers and cryptography.

At the macroscopic level, these effects are not observed: the objects we are used to are always in a single concrete state.

Now for a thought experiment. We take the cat and put it in the box. We also place a flask with a poisonous gas, a radioactive atom and a Geiger counter there. A radioactive atom can decay at any moment, or it may not decay. If it decays, the counter will detect radiation, a simple mechanism will break the flask with gas, and our cat will die. If not, the cat will remain alive.

We close the box. From this moment, from the point of view of quantum mechanics, our atom is in a state of uncertainty - it decayed with a probability of 50% and did not decay with a probability of 50%. Before we open the box and look there (make an observation), it will be in both states at once. And since the fate of the cat directly depends on the state of this atom, it turns out that the cat is literally alive and dead at the same time ("... smearing a living and dead cat (sorry for the expression) in equal shares ..." - writes the author of the experiment). This is how quantum theory would describe this situation.

Schrödinger hardly knew what a fuss his idea would make. Of course, the experiment itself, even in the original, was described extremely roughly and without pretense of scientific accuracy: the author wanted to convey to his colleagues the idea that the theory should be supplemented with clearer definitions of such processes as "observation" in order to exclude scenarios with cats in boxes from its jurisdiction.

The idea of a cat was even used to "prove" the existence of God as a superintelligence, making our very existence possible by his continuous observation. In reality, "observation" does not require a conscious observer, which deprives quantum effects of some degree of mysticism. But even so, quantum physics remains the front of science today with many unexplained phenomena and their interpretations.

Ivan Boldin
PhD in Physics and Mathematics, Researcher, graduate of the Moscow Institute of Physics and Technology

The behavior of objects of the microcosm ( elementary particles, atoms, molecules) significantly differs from the behavior of objects with which we usually have to deal. For example, an electron can fly simultaneously through two spatially distant places or is simultaneously in several orbits in an atom. To describe these phenomena, a theory was created - quantum physics. According to this theory, for example, particles can be smeared in space, but if you want to determine where the particle is after all, then you will always find in some place the whole particle as a whole, that is, it will seem to collapse from its smeared state to a certain place. That is, it is believed that until you have measured the position of a particle, it has no position at all, and physics can only predict with what probability in what place you can find a particle.

Erwin Schrödinger, one of the founders of quantum physics, asked the question: what if, depending on the result of measuring the state of a microparticle, an event occurs or does not occur. For example, this could be implemented as follows: a radioactive atom with a half-life of, say, an hour is taken. An atom can be placed in an opaque box, put there a device that, when the products of the radioactive decay of an atom hit it, breaks an ampoule with a poisonous gas, and put a cat in this box. Then you will not see from the outside whether the atom has decayed or not, that is, according to quantum theory, it simultaneously decayed and did not decay, and the cat, therefore, is simultaneously alive and dead. This cat was called Schrödinger's cat.

It may seem surprising that a cat can be alive and dead at the same time, although formally there is no contradiction here and this is not a refutation of quantum theory. However, questions may arise, for example: who can collapse an atom from a smeared state into a certain state, and who, with such an attempt, goes into a smeared state? How does this collapse process proceed? Or how is it that the one who performs the collapse does not himself obey the laws of quantum physics? Whether these questions make sense, and if so, what are the answers to them is still unclear.

George panin
graduated from the Russian Chemical Technical University named after DI. Mendeleeva, chief specialist of the research department (marketing research)

Now about the cat. Everyone knows that cats love to hide in boxes (thequestion.ru). Erwin Schrödinger was also aware. Moreover, with purely Nordic fanaticism, he used this feature in a famous thought experiment. Its essence was that a cat was locked in a box with a hellish machine. The machine is connected via a relay to a quantum system, for example, a radioactively decaying substance. The probability of decay is known and amounts to 50%. The infernal machine is triggered when the quantum state of the system changes (decay occurs) and the cat dies completely. If we provide the system "Cat-box-hellish machine-quanta" to itself for one hour and remember that the state of a quantum system is described in terms of probability, then it becomes clear that it will probably not work to find out whether the cat is alive or not at a given moment in time. just as it will not work out to accurately predict the fall of a coin heads or tails in advance. The paradox is very simple: the wave function describing a quantum system mixes in itself two states of a cat - it is alive and dead at the same time, just as a bound electron with equal probability can be located anywhere in space equidistant from an atomic nucleus. If we don't open the box, we don't know exactly how the cat is there. Without making observations (read measurements) over an atomic nucleus, we can describe its state only by a superposition (mixing) of two states: a decayed and non-decayed nucleus. A nuclear-dependent cat is both alive and dead at the same time. The question is: when does the system cease to exist as a mixture of two states and choose one specific one?

Of course, when Professor Erwin, back in 1935, conceived his cat-mockery, it was an ingenious way to show the imperfection of quantum mechanics. Indeed, a cat cannot be alive and dead at the same time. As a result of one of the interpretations of the experiment, the contradiction between the laws of the macro-world (for example, the second law of thermodynamics - the cat is either alive or dead) and the micro-world (the cat is alive and dead at the same time) became obvious.

Another most recent interpretation of Schrödinger's thought experiment is a story by Sheldon Cooper, the hero of the TV series Big Bang Theory, which he recited for Penny's less educated roommate. The essence of Sheldon's story is that the concept of Schrödinger's cat can be applied in relationships between people. In order to understand what is happening between a man and a woman, what kind of relationship between them: good or bad, you just need to open the box. Before that, the relationship is both good and bad. youtube.com

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Schrödinger has managed to gain a reputation as an eccentric even among colleagues who themselves are often out of touch with life. The scientist dressed so casually that they did not want to let him into the hotel, because he was mistaken for a vagabond. Once at an important conference, Schrödinger refused to talk about nuclear energy and gave a lecture on philosophy.

Such an ambiguous person decided to troll the scientific community and came up with a cruel experiment involving a cat and a deadly gas. Fortunately, not a single cat was hurt. And all because the experiment was mental and everything happened only in the imagination of a single physicist.

A few words about quantum mechanics

Here's a simple example of how quantum physics works. Take 2 empty matchboxes. Put a match in one of them - this is the object of our familiar macrocosm. Now you can say that the match is only in one box, and there is nothing in the other. This is how the familiar Newtonian physics works.

Everything changes if instead of a match you take an electron: it will be simultaneously in 2 boxes. This is how the laws of quantum physics work.

In 1935, the physicist conducted his famous thought experiment. The original text is in German. Well, we have translated it for you from the language of scientists into the language of ordinary people.

A cat is placed in a closed steel box.
In addition to the cat, there is a hellish machine in the box with a radioactive core and poisonous gas. The gas is in a sealed glass container.
A radioactive nucleus can decay within 1 hour. Or it may not disintegrate. The probability of an event is 50%. (Note: nuclear decay is the easiest example that came to a scientist's mind, because in this case the nucleus has only 2 options. If he took some other variable, the results of the experiment would be difficult to predict.)
If the nucleus decays, the cat is out of luck. Because the decay of the nucleus will be recorded by the Geiger counter, the relay will work, and a special hammer will break the ampoule with the toxic gas. The cat is dead.
If the nucleus does not disintegrate, the cat remains alive.

To understand the essence of Schrödinger's experiment, you need to get acquainted with another principle of quantum mechanics - the observer's paradox .

The radioactive nucleus that threatens our cat is in superposition exactly as long as we do not observe behind the system. As soon as an observer connects to the system and tries to see what is happening in general, the nucleus (atoms, photons) is finally determined and takes a certain position.

If no one is watching the system (does not climb into the box with its measuring instruments), then the core disintegrated / did not disintegrate simultaneously.

But a cat is a completely different matter. He's definitely alive, or he's definitely dead. Because a cat, i.e. a macrosystem, is not affected by quantum laws - it consists of many different particles. The radioactive core is in one world, and the cat lives in the world of big things.

The cat doesn't care when you open the lid. This core will decay / will not decay when the observer appears. And the cat will either be alive or dead regardless of whether you look at it or not.

How does the kernel "know" that it is being watched? When people or devices start observing or measuring, the particles experience a wave (quantum) collapse: for some time they were in a state of uncertainty (they had many options), and the measurement / observation determines the position of the nucleus in space / time. In simple words, the core from the microcosm enters the macrocosm. It leaves the zone of operation of the laws of quantum physics and falls under the influence of Newtonian physics.