Living and dead Schrödinger's cat play. Schrödinger theory in simple words

"Anyone who isn't shocked by quantum theory, does not understand it,” said Niels Bohr, founder quantum theory.
The basis of classical physics is the unambiguous programming of the world, otherwise Laplace determinism, with the advent quantum mechanics was replaced by the invasion of a world of uncertainties and probabilistic events. And here thought experiments came in handy for theoretical physicists. These were the touchstones on which the latest ideas were tested.

"Schrodinger's Cat" is a thought experiment, proposed by Erwin Schrödinger, with whom he wanted to show the incompleteness of quantum mechanics in the transition from subatomic systems to macroscopic systems.

IN closed box cat placed The box contains a mechanism containing a radioactive nucleus and a container with poisonous gas. The probability that the nucleus will decay in 1 hour is 1/2. If the nucleus disintegrates, it activates the mechanism, it opens a container of gas, and the cat dies. According to quantum mechanics, if no observation is made of the nucleus, then its state is described by a superposition (mixing) of two states - a decayed nucleus and an undecayed nucleus, therefore, a cat sitting in a box is both alive and dead at the same time. If the box is opened, then the experimenter can see only one specific state - “the nucleus has decayed, the cat is dead” or “the nucleus has not decayed, the cat is alive.”

When does the system cease to exist? How does one mix two states and choose one specific one?

Purpose of the experiment- show that quantum mechanics is incomplete without some rules indicating under what conditions collapse occurs wave function(an instantaneous change in the quantum state of an object that occurs during measurement), and the cat either becomes dead or remains alive, but ceases to be a mixture of both.

Since it is clear that a cat must be either alive or dead (there is no state intermediate between life and death), this means that this is also true for atomic nucleus. It will necessarily be either decayed or undecayed.

Schrödinger's paper "Current situation in quantum mechanics" with presentation thought experiment appeared with a cat in a German magazine " Natural Sciences” in 1935 to discuss the EPR paradox.

Articles by Einstein-Podolsky-Rosen and Schrödinger indicated the strange nature of " quantum entanglement"(the term was introduced by Schrödinger), characteristic of quantum states, which are a superposition of the states of two systems (for example, two subatomic particles).

Interpretations of quantum mechanics

During the existence of quantum mechanics, scientists have put forward different interpretations of it, but the most supported of all today are the “Copenhagen” and “many-worlds” ones.

"Copenhagen Interpretation"- this interpretation of quantum mechanics was formulated by Niels Bohr and Werner Heisenberg during collaboration in Copenhagen (1927). Scientists have tried to answer questions arising from the wave-particle duality inherent in quantum mechanics, in particular the question of measurement.

IN Copenhagen interpretation the system ceases to be a mixture of states and chooses one of them at the moment when the observation occurs. The experiment with the cat shows that in this interpretation the nature of this very observation - measurement - is not sufficiently defined. Some believe that experience suggests that as long as the box is closed, the system is in both states simultaneously, in a superposition of the states “decayed nucleus, dead cat” and “undecayed nucleus, living cat,” and when the box is opened, then only then does the wave function collapse to one of the options. Others guess that the "observation" occurs when a particle from the nucleus hits the detector; however (and this key moment thought experiment) in the Copenhagen interpretation there is no clear rule that says when this happens, and therefore this interpretation is incomplete until such a rule is introduced into it, or is told how it can be introduced. The exact rule is that randomness appears at the point where the classical approximation is first used.

Thus, we can rely on the following approach: in macroscopic systems we do not observe quantum phenomena (except for the phenomenon of superfluidity and superconductivity); therefore, if we impose a macroscopic wave function on a quantum state, we must conclude from experience that the superposition breaks down. And although it is not entirely clear what it means for something to be “macroscopic” in general, what is certain about a cat is that it is a macroscopic object. Thus, the Copenhagen interpretation does not consider that the cat is in a state of confusion between living and dead before the box is opened.

In the "many worlds interpretation" quantum mechanics, which does not consider the measurement process to be something special, both states of the cat exist, but decohere, i.e. a process occurs in which a quantum mechanical system interacts with its environment and acquires information available in the environment, or otherwise becomes “entangled” with the environment. And when the observer opens the box, he becomes entangled with the cat and from this two states of the observer are formed, corresponding to a living and a dead cat, and these states do not interact with each other. The same mechanism of quantum decoherence is important for “joint” histories. In this interpretation, only a “dead cat” or a “live cat” can be in a “shared story.”

In other words, when the box is opened, the universe splits into two different universes, one in which the observer is looking at a box with a dead cat, and in the other, the observer is looking at a living cat.

The paradox of "Wigner's friend"

Wigner's Friend's Paradox is a complicated experiment of the Schrödinger's cat paradox. Laureate Nobel Prize, American physicist Eugene Wigner introduced the category of “friends”. After completing the experiment, the experimenter opens the box and sees a live cat. The state of the cat at the moment of opening the box goes into the state “the nucleus has not decayed, the cat is alive.” Thus, in the laboratory the cat was recognized as alive. There is a "friend" outside the laboratory. The friend does not yet know whether the cat is alive or dead. The friend recognizes the cat as alive only when the experimenter tells him the outcome of the experiment. But all the other “friends” have not yet recognized the cat as alive, and they will only recognize it when they are told the result of the experiment. Thus, the cat can be recognized as fully alive only when all people in the Universe know the result of the experiment. Until this moment, on the scale of the Big Universe, the cat remains half-alive and half-dead at the same time.

The above is applied in practice: in quantum computing and in quantum cryptography. A light signal in a superposition of two states is sent through a fiber-optic cable. If attackers connect to the cable somewhere in the middle and make a signal tap there in order to eavesdrop on the transmitted information, then 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 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. This makes it possible to create means of communication that exclude undetectable signal interception and eavesdropping.

The experiment (which can in principle be carried out, although working quantum cryptography systems capable of transmitting large amounts of information have not yet been created) also shows that “observation” in the Copenhagen interpretation has no relation to the consciousness of the observer, since in in this case A completely inanimate branch of the wire leads to a change in statistics at the end of the cable.

And in quantum computing, the Schrödinger cat state is a special entangled state of qubits in which they are all in the same superposition of all zeros or ones.

("Qubit" is the smallest element for storing information in a quantum computer. It admits two eigenstates, but it can also be in their superposition. Whenever the state of a qubit is measured, it randomly transitions to one of its own states.)

In reality! Little brother of "Schrodinger's cat"

It's been 75 years since Schrödinger's cat appeared, but still some of the consequences of quantum physics seem at odds with our everyday ideas about matter and its properties. According to the laws of quantum mechanics, it should be possible to create a “cat” state in which it is both alive and dead, i.e. will be in a state of quantum superposition of two states. However, in practice, the creation of a quantum superposition of such large quantity atoms have not yet been achieved. The difficulty is that the more atoms there are in a superposition, the less stable this state is, since external influences tend to destroy it.

To physicists from the University of Vienna (publication in the journal Nature Communications", 2011) for the first time in the world it was possible to demonstrate the quantum behavior of an organic molecule consisting of 430 atoms and in a state of quantum superposition. The molecule obtained by the experimenters looks more like an octopus. The size of the molecules is about 60 angstroms, and the de Broglie wavelength for the molecule was only 1 picometer. This “molecular octopus” was able to demonstrate the properties inherent in Schrödinger’s cat.

Quantum suicide

Quantum suicide is a thought experiment in quantum mechanics that was proposed independently by G. Moravec and B. Marshall, and was expanded in 1998 by cosmologist Max Tegmark. This thought experiment, a modification of the Schrödinger's cat thought experiment, clearly shows the difference between two interpretations of quantum mechanics: the Copenhagen interpretation and the Everett many-worlds interpretation.

The experiment is actually an experiment with Schrödinger's cat from the cat's point of view.

In the proposed experiment, a gun is pointed at the participant, which fires or does not fire depending on the decay of some radioactive atom. There is a 50% chance that the gun will go off and the participant will die. If the Copenhagen interpretation is correct, then the gun will eventually go off and the participant will die.
If Everett’s many-worlds interpretation is correct, then as a result of each experiment performed, the universe splits into two universes, in one of which the participant remains alive, and in the other dies. In worlds where a participant dies, he ceases to exist. In contrast, from the perspective of the non-dead participant, the experiment will continue without causing the participant to disappear. This happens because in any branch the participant is able to observe the result of the experiment only in the world in which he survives. And if the many-worlds interpretation is correct, then the participant may notice that he will never die during the experiment.

The participant will never be able to talk about these results, since from the point of view of an outside observer, the probability of the outcome of the experiment will be the same in both the many-worlds and the Copenhagen interpretations.

Quantum immortality

Quantum immortality is a thought experiment that stems from the quantum suicide thought experiment and states that, according to the many-worlds interpretation of quantum mechanics, beings that have the capacity for self-awareness are immortal.

Let's imagine that a participant in an experiment detonates a nuclear bomb near him. In almost all parallel Universes, a nuclear explosion will destroy the participant. But despite this, there must be a small number of alternative Universes in which the participant somehow survives (that is, Universes in which a potential rescue scenario is possible). The idea of ​​quantum immortality is that the participant remains alive, and thereby is able to perceive the surrounding reality, in at least one of the Universes in the set, even if the number of such universes is extremely small compared to the number of all possible Universes. Thus, over time, the participant will discover that he can live forever. Some parallels to this conclusion can be found in the concept of the anthropic principle.

Another example stems from the idea of ​​quantum suicide. In this thought experiment, the participant points a gun at himself, which may or may not fire depending on the outcome of the decay of some radioactive atom. There is a 50% chance that the gun will go off and the participant will die. If the Copenhagen interpretation is correct, then the gun will eventually go off and the participant will die.

If Everett’s many-worlds interpretation is correct, then as a result of each experiment conducted, the universe splits into two universes, in one of which the participant remains alive, and in the other dies. In worlds where a participant dies, he ceases to exist. On the contrary, from the point of view of the non-dead participant, the experiment will continue without causing the participant to disappear, since after each split of universes he will be able to recognize himself only in those universes where he survived. Thus, if Everett's many-worlds interpretation is correct, then the participant may notice that he will never die in the experiment, thereby "proving" his immortality, at least from his point of view.

Proponents of quantum immortality point out that this theory does not contradict any known laws physicists (this position is far from unanimously accepted in scientific world). In their reasoning, they rely on the following two controversial assumptions:
- Everett's many-worlds interpretation is correct, not the Copenhagen interpretation, since the latter denies the existence parallel universes;
- all possible scenarios in which a participant may die during the experiment contain at least a small subset of scenarios in which the participant remains alive.

A possible argument against the theory of quantum immortality is that the second assumption does not necessarily follow from Everett's many-worlds interpretation, and it may conflict with the laws of physics, which are believed to apply to all possible realities. The many-worlds interpretation of quantum physics does not necessarily imply that “anything is possible.” It only indicates that at a certain point in time the universe can be divided into a number of others, each of which will correspond to one of the many possible outcomes. For example, the second law of thermodynamics is believed to apply to all probable universes. This means that, theoretically, the existence of this law prevents the formation of parallel universes where it would be violated. The consequence of this may be the achievement, from the point of view of the experimenter, of a state of reality where his further survival becomes impossible, since this would require a violation of the law of physics, which, according to the previously stated assumption, is valid for all possible realities.

For example, in an explosion nuclear bomb described above, it is quite difficult to describe a plausible scenario that does not violate basic biological principles in which the participant will survive. Living cells simply cannot exist at the temperatures reached in the center nuclear explosion. In order for the theory of quantum immortality to remain valid, it is necessary that either a misfire occurs (and thereby avoid a nuclear explosion), or some event occurs that is based on as yet undiscovered or unproven laws of physics. Another argument against the theory under discussion can be the presence of natural biological death in all creatures, which cannot be avoided in any of the parallel Universes (at least in at this stage development of science)

On the other hand, the second law of thermodynamics is a statistical law, and nothing is contradicted by the occurrence of fluctuations (for example, the appearance of a region with conditions suitable for the life of an observer in a universe that has generally reached a state of thermal death; or, in principle, the possible movement of all particles resulting from nuclear explosion, in such a way that each of them will fly past the observer), although such a fluctuation will occur only in an extremely small part of all possible outcomes. The argument regarding the inevitability of biological death can also be refuted on the basis of probabilistic considerations. For every living organism in this moment time there is a non-zero probability that he will remain alive during the next second. Thus, the probability that he will remain alive for the next billion years is also non-zero (since it is the product large number non-zero factors), although very small.

What is problematic about the idea of ​​quantum immortality is that according to it, a self-aware being will be “forced” to experience extremely unlikely events that will arise in situations in which the participant would seem to die. Even though in many parallel universes the participant dies, the few universes that the participant is able to subjectively perceive will develop in an extremely unlikely scenario. This, in turn, may in some way cause a violation of the principle of causality, the nature of which in quantum physics is not yet clear enough.

Although the idea of ​​quantum immortality stems largely from the “quantum suicide” experiment, Tegmark argues that under any normal conditions, every thinking being before death goes through a stage (from a few seconds to several years) of decreasing level of self-awareness, which has nothing to do with quantum mechanics, and the participant has no possibility of continued existence by moving from one world to another, giving him the opportunity to survive.

Here, a self-conscious intelligent observer only in a relatively small number of possible states in which he retains self-consciousness continues to remain in, so to speak, “ healthy body" The possibility that the observer, while retaining consciousness, will remain crippled is much greater than if he remains unharmed. Any system (including a living organism) has much more possibilities function incorrectly than to remain in perfect shape. Boltzmann's ergodic hypothesis requires that the immortal observer will sooner or later go through all states compatible with the preservation of consciousness, including those in which he will feel unbearable suffering - and there will be significantly more such states than states of optimal functioning of the organism. Thus, as philosopher David Lewis suggests, we should hope that the many-worlds interpretation is wrong.

To my shame, I want to admit that I heard this expression, but did not know what it meant or even on what topic it was used. Let me tell you what I read on the Internet about this cat... -

« Shroedinger `s cat“- this is the name of the famous thought experiment of the famous Austrian theoretical physicist Erwin Schrödinger, who is also a Nobel Prize laureate. With the help of this fictitious experiment, the scientist wanted to show the incompleteness of quantum mechanics in the transition from subatomic systems to macroscopic systems.

The original article by Erwin Schrödinger was published in 1935. In it, the experiment was described using or even personifying:

You can also construct cases in which there is quite a burlesque. Let some cat be locked in a steel chamber with the following diabolical machine (which should be regardless of the cat's intervention): inside a Geiger counter there is a tiny amount of radioactive substance, so small that only one atom can decay in an hour, but with the same most likely it may not disintegrate; if this happens, the reading tube is discharged and the relay is activated, releasing the hammer, which breaks the flask with hydrocyanic acid.

If we leave this entire system to itself for an hour, then we can say that the cat will be alive after this time, as long as the atom does not disintegrate. The first atomic decay would poison the cat. The psi-function of the system as a whole will express this by mixing or smearing a living and a dead cat (pardon the expression) in equal parts. It is typical in such cases that the uncertainty initially limited atomic world, is converted into macroscopic uncertainty, which can be eliminated by direct observation. This prevents us from naively accepting the “blur model” as reflecting reality. This in itself does not mean anything unclear or contradictory. There's a difference between a blurry or out-of-focus photo and a photo of clouds or fog.

In other words:

1. There is a box and a cat. The box contains a mechanism containing a radioactive atomic nucleus and a container of poisonous gas. The experimental parameters were selected so that the probability of nuclear decay in 1 hour is 50%. If the nucleus disintegrates, a container of gas opens and the cat dies. If the nucleus does not decay, the cat remains alive and well.
2. We close the cat in a box, wait an hour and ask the question: is the cat alive or dead?
3. Quantum mechanics seems to tell us that the atomic nucleus (and therefore the cat) is in all possible states simultaneously (see quantum superposition). Before we open the box, the cat-core system is in the state “the nucleus has decayed, the cat is dead” with a probability of 50% and in the state “the nucleus has not decayed, the cat is alive” with a probability of 50%. It turns out that the cat sitting in the box is both alive and dead at the same time.
4. According to the modern Copenhagen interpretation, the cat is alive/dead without any intermediate states. And the choice of the decay state of the nucleus occurs not at the moment of opening the box, but even when the nucleus enters the detector. Because the reduction of the wave function of the “cat-detector-nucleus” system is not associated with the human observer of the box, but is associated with the detector-observer of the nucleus.

According to quantum mechanics, if the nucleus of an atom is not observed, then its state is described by a mixture of two states - a decayed nucleus and an undecayed nucleus, therefore, a cat sitting in a box and personifying the nucleus of an atom is both alive and dead at the same time. If the box is opened, then the experimenter can see only one specific state - “the nucleus has decayed, the cat is dead” or “the nucleus has not decayed, the cat is alive.”

The essence in human language: Schrödinger's experiment showed that, from the point of view of quantum mechanics, the cat is both alive and dead, which cannot be. Therefore, quantum mechanics has significant flaws.

The question is: when does a system cease to exist as a mixture of two states and choose one specific one? The purpose of the experiment is to show that quantum mechanics is incomplete without some rules that indicate under what conditions the wave function collapses and the cat either becomes dead or remains alive but is no longer a mixture of both. Since it is clear that a cat must be either alive or dead (there is no state intermediate between life and death), this will be similar for the atomic nucleus. It must be either decayed or undecayed ().

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

Below is a video clip of this Big Bang Theory exchange between Sheldon and Penia.

Schrödinger's illustration is best example to describe the main paradox of quantum physics: according to its laws, particles such as electrons, photons and even atoms exist in two states simultaneously (“alive” and “dead”, if you remember the long-suffering cat). These states are called.

American physicist Art Hobson () from the University of Arkansas (Arkansas State University) proposed his solution to this paradox.

“Measurements in quantum physics are based on the operation of certain macroscopic devices, such as a Geiger counter, with the help of which the quantum state of microscopic systems - atoms, photons and electrons is determined. Quantum theory implies that if you connect a microscopic system (particle) to some macroscopic device that distinguishes two different states of the system, then the device (Geiger counter, for example) will go into a state of quantum entanglement and also find itself in two superpositions at the same time. However, it is impossible to observe this phenomenon directly, which makes it unacceptable,” says the physicist.

Hobson says that in Schrödinger's paradox, the cat plays the role of a macroscopic device, a Geiger counter, connected to a radioactive nucleus to determine the state of decay or “non-decay” of that nucleus. In this case, a living cat will be an indicator of “non-decay”, and a dead cat will be an indicator of decay. But according to quantum theory, the cat, like the nucleus, must exist in two superpositions of life and death.

Instead, according to the physicist, the cat's quantum state should be entangled with the state of the atom, meaning that they are in a "nonlocal relationship" with each other. That is, if the state of one of the entangled objects suddenly changes to the opposite, then the state of its pair will also change, no matter how far they are from each other. In doing so, Hobson refers to this quantum theory.

“The most interesting thing about the theory of quantum entanglement is that the change in state of both particles occurs instantly: no light or electromagnetic signal would have time to transmit information from one system to another. So you could say it's one object divided into two parts by space, no matter how great the distance between them is,” explains Hobson.

Schrödinger's cat is no longer alive and dead at the same time. He is dead if the disintegration occurs, and alive if the disintegration never happens.

Let us add that similar solutions to this paradox were proposed by three more groups of scientists over the past thirty years, but they were not taken seriously and remained unnoticed in broad scientific circles. Hobson that the solution to the paradoxes of quantum mechanics, at least theoretically, is absolutely necessary for its deep understanding.

Schrödinger

But just recently, THEORISTS EXPLAINED HOW GRAVITY KILLS SCHRODINGER'S CAT, but this is more complicated...-

As a rule, physicists explain the phenomenon that superposition is possible in the world of particles, but is impossible with cats or other macro-objects, interference from environment. When a quantum object passes through a field or interacts with random particles, it immediately assumes just one state - as if it were measured. This is exactly how the superposition is destroyed, as scientists believed.

But even if somehow it became possible to isolate a macro-object in a state of superposition from interactions with other particles and fields, it would still sooner or later take on a single state. At least this is true for processes occurring on the surface of the Earth.

“Somewhere in interstellar space, perhaps a cat would have a chance, but on Earth or near any planet this is extremely unlikely. And the reason for this is gravity,” explains the lead author of the new study, Igor Pikovsky () from the Harvard-Smithsonian Center for Astrophysics.

Pikovsky and his colleagues from the University of Vienna argue that gravity has a destructive effect on quantum superpositions of macro-objects, and therefore we do not observe similar phenomena in the macrocosm. The basic concept of the new hypothesis, by the way, is feature film"-Interstellar"-.

Einstein's theory of general relativity states that an extremely massive object will bend spacetime around it. Considering the situation at a smaller level, we can say that for a molecule placed near the surface of the Earth, time will pass somewhat slower than for one located in the orbit of our planet.

Due to the influence of gravity on space-time, a molecule affected by this influence will experience a deviation in its position. And this, in turn, should affect its internal energy - vibrations of particles in a molecule that change over time. If a molecule is introduced into a state of quantum superposition of two locations, then the relationship between position and internal energy would soon force the molecule to “select” only one of two positions in space.

“-In most cases, the phenomenon of decoherence is associated with external influence, but in this case, the internal vibration of the particles interacts with the movement of the molecule itself,” explains Pikovsky.

This effect has not yet been observed, since other sources of decoherence, such as magnetic fields, thermal radiation and the vibrations are usually much stronger, causing the destruction of quantum systems long before gravity does. But experimenters strive to test the hypothesis.

A similar setup could also be used to test the ability of gravity to destroy quantum systems. To do this, it will be necessary to compare vertical and horizontal interferometers: in the first, the superposition should soon disappear due to the dilation of time at different “heights” of the path, while in the second, the quantum superposition may remain.

sources

http://4brain.ru/blog/%D0%BA%D0%BE%D1%82-%D1%88%D1%80%D0%B5%D0%B4%D0%B8%D0%BD%D0% B3%D0%B5%D1%80%D0%B0-%D1%81%D1%83%D1%82%D1%8C-%D0%BF%D1%80%D0%BE%D1%81%D1% 82%D1%8B%D0%BC%D0%B8-%D1%81%D0%BB%D0%BE%D0%B2%D0%B0%D0%BC%D0%B8/

http://www.vesti.ru/doc.html?id=2632838

Here's a little more pseudo-scientific: for example, and here. If you don’t know yet, read about and what it is. And we’ll find out what

Although planetary model atom has proven its worth, the theory existing at that time could not fully explain all processes, which were observed in real life. It turned out that in reality, for some reason, classical Newtonian mechanics does not work at the micro level. Those. the prototype model, borrowed from real life, does not correspond to the observations of scientists of that time in the case of considering the atom instead of our solar system.

Based on this, the concept was significantly redesigned. There was such a discipline as quantum mechanics. The origins of this direction were the outstanding physicist Erwin Schrödinger.

Concept of superposition

The main principle that distinguishes new theory, is superposition principle. According to this principle, a quantum (electron, photon or proton) can be in two states at the same time. If make it easier to understand this formulation, we get a fact that is completely impossible to imagine in our minds. A quantum can be in two places at the same time.

At the time of its appearance, this theory contradicted not only classical mechanics, but also common sense. Even now, an educated person far from physics can hardly imagine such a situation. After all, this understanding ultimately implies that he himself the reader can be here and there now. This is exactly how a person tries to imagine the transition from the macroworld to the microworld.

For a person who was accustomed to experiencing the action of Newtonian mechanics and perceiving himself at one point in space, it was extremely difficult to imagine being in two places at once. Besides, there was no theory or patterns as such during the transition from macro to micro. There was no understanding of specific numerical values and rules.

However, the instruments of that time made it possible to clearly record this “quantum dissonance”. Laboratory instruments confirmed that the formulated postulates are indeed consistent and the quantum is capable of being in two states. For example, electron gas around the nucleus of an atom was detected.

Based on this, Schrödinger formulated a famous concept that is now known as the cat theory. The purpose of this formulation was to show that in classical theory physics, a huge gap has formed that requires additional study.

Shroedinger `s cat

The thought experiment about the cat was that the cat was placed in a closed steel box. The box was equipped a device with a poisonous gas and a device with an atomic nucleus.

Based on known postulates, the nucleus of an atom may disintegrate into components within one hour, but may not disintegrate. Accordingly, the probability of this event is 50%.

If the nucleus decays, then the counter-recorder is triggered, and in response to this event, a release occurs toxic substance from the previously described device with which the box is equipped. Those. the cat dies from poison. If this does not happen, the cat does not die accordingly. Based on a 50% chance of decay, the cat has a 50% chance of surviving.

Based on quantum theory, an atom can be in two states at once. Those. the atom both decayed and did not decay. This means that the recorder worked, breaking the container with poison, and did not disintegrate. The cat was poisoned by poison, and the cat was not poisoned by poison at the same time.

But it is simply impossible to imagine such a picture that upon opening the box, the researcher discovered both a dead and a living cat. The cat is either alive or dead. This is the paradox of the situation. It is impossible for the viewer's consciousness to imagine a dead-alive cat.

The paradox is that the cat is an object of the macrocosm. Accordingly, to say about him that he is alive and dead, i.e. is in two states at once, similar to a quantum, will not be entirely correct.

Using this example, Schrödinger concentrated specifically on the fact that there are no clear parallels between the macro- and microworlds. Subsequent comments given by experts explain that a radiation detector-cat system should be considered, not a cat-spectator system. In a detector-cat system, only one event is likely.

In 1935 great physicist, Nobel laureate and the founder of quantum mechanics, Erwin Schrödinger, formulated his famous paradox.

The scientist suggested that if you take a certain cat and place it in an opaque steel box with an “infernal machine,” then in an hour it will be alive and dead at the same time. The mechanism in the box looks like this: inside the Geiger counter there is a microscopic amount of a radioactive substance that can decay into only one atom in an hour; at the same time, with the same probability it may not decay. If decay does occur, then the lever mechanism will work and the hammer will break the vessel with hydrocyanic acid and the cat will die; if there is no decay, then the vessel will remain intact, and the cat will be alive and well.

If we were not talking about a cat and a box, but about the world of subatomic particles, then scientists would say that the cat is both alive and dead at the same time, but in the macrocosm such a conclusion is incorrect. So why do we operate with such concepts when we are talking about smaller particles of matter?

Schrödinger's illustration is the best example to describe the main paradox of quantum physics: according to its laws, particles such as electrons, photons and even atoms exist in two states at the same time ("alive" and "dead", if you remember the long-suffering cat). These states are called superpositions.

American physicist Art Hobson from the University of Arkansas (Arkansas State University) proposed his solution to this paradox.

“Measurements in quantum physics are based on the operation of certain macroscopic devices, such as a Geiger counter, with the help of which the quantum state of microscopic systems - atoms, photons and electrons is determined. Quantum theory implies that if you connect a microscopic system (particle) to some macroscopic device, distinguishing two different states of the system, then the device (Geiger counter, for example) will go into a state of quantum entanglement and also find itself in two superpositions at the same time. However, it is impossible to observe this phenomenon directly, which makes it unacceptable,” says the physicist.

Hobson says that in Schrödinger's paradox, the cat plays the role of a macroscopic device, a Geiger counter, connected to a radioactive nucleus to determine the state of decay or "non-decay" of that nucleus. In this case, a living cat will be an indicator of “non-decay”, and a dead cat will be an indicator of decay. But according to quantum theory, the cat, like the nucleus, must exist in two superpositions of life and death.

Instead, according to the physicist, the cat's quantum state should be entangled with the state of the atom, meaning that they are in a "nonlocal connection" with each other. That is, if the state of one of the entangled objects suddenly changes to the opposite, then the state of its pair will also change, no matter how far they are from each other. In doing so, Hobson refers to this quantum theory.

“The most interesting thing about the theory of quantum entanglement is that the change of state of both particles occurs instantly: no light or electromagnetic signal would have time to transmit information from one system to another. Thus, we can say that this is one object divided into two parts space, no matter how great the distance between them,” explains Hobson.

Schrödinger's cat is no longer alive and dead at the same time. He is dead if the disintegration occurs, and alive if the disintegration never happens.

Let us add that similar solutions to this paradox were proposed by three more groups of scientists over the past thirty years, but they were not taken seriously and remained unnoticed in broad scientific circles. Hobson notes that solving the paradoxes of quantum mechanics, at least theoretically, is absolutely necessary for its deep understanding.

Can a cat be both alive and dead at the same time? How many parallel universes are there? And do they even exist? These are not science fiction questions at all, but very real ones. scientific problems, solved by quantum physics.

So let's start with Schrödinger's cat. This is a thought experiment proposed by Erwin Schrödinger to point out a paradox that exists in quantum physics. The essence of the experiment is as follows.

An imaginary cat is simultaneously placed in a closed box, as well as the same imaginary mechanism with a radioactive core and a container of poisonous gas. According to the experiment, if the nucleus disintegrates, it will activate the mechanism: the gas container will open and the cat will die. The probability of nuclear decay is 1 in 2.

The paradox is that, according to quantum mechanics, if the nucleus is not observed, then the cat is in a so-called superposition, in other words, the cat is simultaneously in mutually exclusive states (it is both alive and dead). However, if the observer opens the box, he can verify that the cat is in one specific state: it is either alive or dead. According to Schrödinger, the incompleteness of quantum theory lies in the fact that it does not specify under what conditions a cat ceases to be in superposition and turns out to be either alive or dead.

This paradox is compounded by Wigner's experiment, which adds the category of friends to an already existing thought experiment. According to Wigner, when the experimenter opens the box, he will know whether the cat is alive or dead. For the experimenter, the cat ceases to be in superposition, but for the friend who is behind the door, and who does not yet know about the results of the experiment, the cat is still somewhere “between life and death.” This can be continued with an infinite number of doors and friends, and according to similar logic, the cat will be in superposition until all people in the Universe know what the experimenter saw when he opened the box.

How does quantum physics explain such a paradox? The quantum physics suggests a thought experiment quantum suicide and two possible options developments of events based on different interpretations of quantum mechanics.

In a thought experiment, a gun is pointed at the participant and either it will fire as a result of the decay of a radioactive atom or it will not. Again, 50 to 50. Thus, the participant in the experiment will either die or not, but for now he is, like Schrödinger’s cat, in superposition.

This situation can be interpreted in different ways from the point of view of quantum mechanics. According to the Copenhagen interpretation, the gun will eventually go off and the participant will die. According to Everett's interpretation, superposition provides for the presence of two parallel universes in which the participant simultaneously exists: in one of them he is alive (the gun did not fire), in the second he is dead (the weapon fired). However, if the many-worlds interpretation is correct, then in one of the universes the participant always remains alive, which leads to the idea of ​​​​the existence of "quantum immortality".

As for Schrödinger’s cat and the observer of the experiment, then, according to Everett’s interpretation, he also finds himself and the cat in two Universes at once, that is, in “quantum language”, “entangled” with him.

This sounds like a story from a science fiction novel, but it is one of many... scientific theories, which takes place in modern physics.