Schrödinger's cat is a famous thought experiment. It was put by the famous Nobel laureate in physics - the Austrian scientist Erwin Rudolf Josef Alexander Schrödinger.
The essence of the experiment was as follows. A cat was placed in a closed chamber (box). The box is equipped with a mechanism that contains a radioactive core and poisonous gas. The parameters are chosen so that the probability of a nuclear decay in one hour is exactly fifty percent. If the core disintegrates, the mechanism will come into action and a container with poisonous gas will open. Therefore, Schrödinger's cat will die.
According to the laws, if you do not observe the nucleus, then its states will be described according to two main states - the nucleus of the decayed and not decayed. And here a paradox arises: Schrödinger's cat, which sits in a box, can be both dead and alive at the same time. But if the box is opened, the experimenter will see only one specific state. Either "the nucleus has disintegrated and the cat is dead" or "the nucleus has not disintegrated and Schrödinger's cat is alive".
Logically, we will have one of two outputs: either a live cat or a dead one. But in the potential the animal is in both states at once. Schrodinger thus tried to prove his opinion about the limitations of quantum mechanics.
According to the Copenhagen interpretation and this experiment in particular, a cat in one of its potential phases (dead-alive) acquires these properties only after an outside observer interferes with the process. But as long as this observer is not present (this implies the presence of a specific person who has the virtues of clarity of vision and consciousness), the cat will be in limbo "between life and death."
The famous ancient parable about a cat walking by itself acquires new, interesting shades in the context of this experiment.
According to Everett, which differs markedly from the classical Copenhagen one, the process of observation is not considered anything special. Both states that Schrödinger's cat can be in can exist in this interpretation. But they decohere with each other. This means that the unity of these states will be violated precisely as a result of interaction with the outside world. It is the observer who opens the box and brings discord into the state of the cat.
There is an opinion that the decisive word in this matter should be left to such a creature as Schrödinger's cat. The meaning of this opinion is the acceptance of the fact that in the whole given experiment it is the animal that is the only absolutely competent observer. For example, scientists Max Tegmark, Bruno Marshal and Hans Moraven presented a modification of the above experiment, where the main point of view is the opinion of the cat. In this case, Schrödinger's cat undoubtedly survives, because only the surviving cat can observe the results. But the scientist Nadav Katz published his results, in which he was able to "return" the state of the particle back after changing its state. Thus, the chances of survival of the cat increase markedly.
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 further 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, as if in nothing never happened, looks off 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 familiar to us are always in a single specific state.
And now a thought experiment. We take a cat and put it in a box. We also place a flask with poisonous gas, a radioactive atom and a Geiger counter there. A radioactive atom may or may not decay at any time. 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 live.
We close the box. From this point on, 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 inside (make an observation), it will be in both states at once. And since the fate of a cat directly depends on the state of this atom, it turns out that the cat is also literally alive and dead at the same time (“... smearing a living and dead cat (sorry for the expression) in equal proportions ...” - writes the author of the experiment). This is how quantum theory would describe this situation.
Schrödinger hardly guessed what a stir his idea would make. Of course, the experiment itself, even in the original, is described extremely rudely and without pretense of scientific accuracy: the author wanted to convey to his colleagues the idea that the theory needs to 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 supermind, which by its continuous observation makes our very existence possible. In reality, "observation" does not require a conscious observer, which deprives quantum effects of some mysticism. But even so, quantum physics remains today the front of science with many unexplained phenomena and their interpretations.
Ivan Boldin
Candidate of Physical and Mathematical Sciences, Researcher, MIPT graduate
The behavior of objects in the microworld (elementary particles, atoms, molecules) differs significantly 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 be 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 the entire particle in some place, that is, it will sort of collapse from its smeared state to some specific place. That is, it is believed that until you measure 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 creators of quantum physics, asked himself the question: what if, depending on the result of measuring the state of a microparticle, some event occurs or does not occur. For example, this could be implemented as follows: a radioactive atom is taken with a half-life of, say, an hour. An atom can be placed in an opaque box, put there a device that, when the products of the radioactive decay of the atom hit it, breaks an ampoule with 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 both alive and dead. Such a cat became known as 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 carry out the collapse of an atom from a smeared state to a certain state, and who, in such an attempt, himself passes 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 RKhTU them. DI. Mendeleev, Chief Specialist of the Research Department (Marketing Research)
As Heisenberg explained to us, due to the uncertainty principle, the description of the objects of the quantum microworld is of a different nature than the usual description of the objects of the Newtonian macrocosm. Instead of spatial coordinates and speed, which we used to describe the mechanical movement of, for example, a ball on a billiard table, in quantum mechanics, objects are described by the so-called wave function. The crest of the "wave" corresponds to the maximum probability of finding a particle in space at the moment 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 with time.
Now about the cat. Everyone knows that cats love to hide in boxes (thequestion.ru). Erwin Schrödinger was also aware. Moreover, with purely Nordic savagery, he used this feature in a famous thought experiment. Its essence was that a cat was locked in a box with an infernal machine. The machine is connected through a relay to a quantum system, for example, a radioactively decaying substance. The decay probability is known and is 50%. The infernal machine works when the quantum state of the system changes (decay occurs) and the cat dies completely. If you leave the “Cat-box-infernal machine-quanta” system to itself for one hour and remember that the state of the quantum system is described in terms of probability, then it becomes clear that it’s probably impossible to find out whether the cat is alive or not, at a given moment in time, just as it will not work out accurately to predict the fall of a coin on heads or tails in advance. The paradox is very simple: the wave function describing a quantum system mixes 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 the atomic nucleus. If we don't open the box, we don't know exactly how the cat is. Without making observations (read measurements) on the atomic nucleus, we can describe its state only by a superposition (mixing) of two states: a decayed and non-decayed nucleus. A nuclear-addicted cat is both alive and dead at the same time. The question is this: when does a system cease to exist as a mixture of two states and chooses one concrete 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 takes place, which is also a measurement (the box opens). That is, the very fact of measurement changes the 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 that accompany it change the reality around us. Personally, this fact makes my 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 sharpness 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 (falling it to one of two probabilistic) states is greatly exaggerated.
Of course, when Professor Erwin conceived his cat-fraud back in 1935, it was a clever way to show the imperfection of quantum mechanics. Indeed, a cat cannot be alive and dead at the same time. As a result, one of the interpretations of the experiment was the obvious contradiction between the laws of the macro-world (for example, the second law of thermodynamics - a cat is either alive or dead) and the micro-world (a cat is alive and dead at the same time).
The above is applied in practice: in quantum computing and in quantum cryptography. A fiber-optic cable sends a light signal that is in a superposition of two states. 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. Having carried out statistical tests of light at the receiving end of the cable, it will be possible to find out whether the light is in a superposition of states or whether it has already been observed and transmitted to another point. This makes it possible to create means of communication that exclude imperceptible signal interception and eavesdropping.
Another most recent interpretation of Schrödinger's thought experiment is the story of Sheldon Cooper, the hero of the Big Bang Theory series, which he spoke to the less educated neighbor Penny. The point of Sheldon's story is that the concept of Schrödinger's cat can be applied to 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. Until then, relationships are both good and bad. youtube.com
Surely you have heard more than once that there is such a phenomenon as "Schrödinger's Cat". But if you are not a physicist, then, most likely, you only remotely imagine what kind of cat it is and why it is needed.
« 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 winner. 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.
In this article, an attempt is made to explain in simple terms the essence of Schrödinger's theory about the cat and quantum mechanics, so that it is accessible to a person who does not have a higher technical education. The article will also present various interpretations of the experiment, including those from the Big Bang Theory series.
Description of the experiment
The original article by Erwin Schrödinger was published in 1935. In it, the experiment was described using or even personified:
You can also construct cases in which burlesque is enough. Let some cat be locked in a steel chamber along with the following diabolical machine (which should be independent of the intervention of the cat): inside the Geiger counter is a tiny amount of radioactive material, so small that only one atom can decay in an hour, but with the same the probability may not fall apart; if this happens, the reading tube is discharged and a relay is activated, lowering the hammer, which breaks the cone of hydrocyanic acid.
If we leave this whole 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 decay. The first decay of an atom would have poisoned the cat. The psi-function of the system as a whole will express this by mixing in itself or smearing the living and dead cat (forgive the expression) in equal proportions. Typical in such cases is that the uncertainty, originally limited to the atomic world, is transformed into a macroscopic uncertainty that can be eliminated by direct observation. This prevents us from naively accepting the "blur model" as reflecting reality. By itself, this does not mean anything unclear or contradictory. There is a difference between a fuzzy or out-of-focus photo and a cloud or fog shot.
In other words:
- 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 are chosen so that the probability of nuclear decay in 1 hour is 50%. If the core disintegrates, the gas container opens and the cat dies. If the disintegration of the nucleus does not occur, the cat remains alive and well.
- We close the cat in a box, wait an hour and ask ourselves: is the cat alive or dead?
- Quantum mechanics, as it were, tells us that the atomic nucleus (and hence the cat) is in all possible states at the same time (see quantum superposition). Before we opened the box, the “cat-core” system is in the state “the core 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.
- According to the modern Copenhagen interpretation, the cat is still 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 connected with the human observer of the box, but is connected with the detector-observer of the nucleus.
Explanation in simple words
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 disintegrated, the cat is dead" or "the nucleus has not disintegrated, the cat is alive."
Essence in human language: Schrödinger's experiment showed that, from the point of view of quantum mechanics, a cat is both alive and dead at the same time, which cannot be. Consequently, quantum mechanics has significant flaws.
The question is this: when does a system cease to exist as a mixture of two states and chooses one concrete one? The purpose of the experiment is to show that quantum mechanics is incomplete without some rules that specify under what conditions the wave function collapses and the cat either becomes dead or remains alive, but ceases to be a mixture of both. Since it is clear that the cat must necessarily be either alive or dead (there is no intermediate state between life and death), this will be the same for the atomic nucleus. It must necessarily be either broken up or not broken up (Wikipedia).
Video from The Big Bang Theory
Another most recent interpretation of Schrödinger's thought experiment is the story of Sheldon Cooper, the hero of the Big Bang Theory series, which he spoke to the less educated neighbor Penny. The point of Sheldon's story is that the concept of Schrödinger's cat can be applied to 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. Until then, relationships are both good and bad.
Below is a video clip of this Big Bang Theory dialogue between Sheldon and Peny.
Was the cat still alive as a result of the experiment?
For those who did not read the article carefully, but still worries about the cat - good news: do not worry, according to our data, as a result of a thought experiment by a crazy Austrian physicist
NOT A SINGLE CAT WERE INJURED
We have all heard about the famous Schrödinger's cat, but do we know what kind of cat it really is? Let's figure it out and try to talk about the famous Schrödinger's cat in simple words.
Schrödinger's cat is an experiment conducted by Erwin Schrödinger, one of the founding fathers of quantum mechanics. Moreover, this is not an ordinary physical experiment, but mental.
It must be admitted that Erwin Schrödinger was a very imaginative man.
So, what do we have as an imaginary basis for the experiment? There is a cat placed in a box. The box also contains a Geiger counter with some very small amounts of radioactive material. The amount of substance is such that the probability of decay and non-decay of one atom within an hour is the same. If the atom decays, a special mechanism will start that will break the flask with hydrocyanic acid, and the poor cat will die. If the collapse does not occur, then the cat will continue to sit quietly in his box and dream of sausages.
What is the essence of Schrödinger's cat? Why even come up with such a surreal experience?
According to the results of the experiment, we will know whether the cat is alive or not only when we open the box. From the point of view of quantum mechanics, a cat simultaneously (like an atom of matter) is in two states at once - both alive and dead at the same time. This is the famous paradox of Schrödinger's cat.
Naturally, this cannot be. Erwin Schrödinger set up this thought experiment to show the imperfection of quantum mechanics when moving from subatomic to macroscopic systems.
Here is Schrödinger's own formulation:
You can also construct cases in which burlesque is enough. Let some cat be locked in a steel chamber, along with the following diabolical machine (which should be independent of the intervention of the cat): inside the Geiger counter is a tiny amount of radioactive material - so small that only one atom can decay in an hour, but with the same the probability may not fall apart; if this happens, the reading tube is discharged and a relay is activated, lowering the hammer, which breaks the cone of hydrocyanic acid.
If we leave this whole 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 decay. The first decay of an atom would have poisoned the cat. The psi-function of the system as a whole will express this by mixing in itself or smearing the living and dead cat (forgive the expression) in equal proportions. Typical in such cases is that the uncertainty, originally limited to the atomic world, is transformed into a macroscopic uncertainty that can be eliminated by direct observation. This prevents us from naively accepting the "blur model" as reflecting reality. By itself, this does not mean anything unclear or contradictory. There is a difference between a fuzzy or out-of-focus photo and a cloud or fog shot.
A definitely positive point in this experiment is the fact that not a single animal was harmed during its course.
Finally, to consolidate the material, we suggest you watch a video from the good old series "The Big Bang Theory".
And if you suddenly have questions or the teacher asked a problem on quantum mechanics, please contact. Together we will solve all issues much faster!
As Heisenberg explained to us, due to the uncertainty principle, the description of the objects of the quantum microworld is of a different nature than the usual description of the objects of the Newtonian macrocosm. Instead of spatial coordinates and speed, which we used to describe the mechanical movement of, for example, a ball on a billiard table, in quantum mechanics, objects are described by the so-called wave function. The crest of the "wave" corresponds to the maximum probability of finding a particle in space at the moment 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 with time.
Now about the cat. Everyone knows that cats love to hide in boxes (). Erwin Schrödinger was also aware. Moreover, with purely Nordic savagery, he used this feature in a famous thought experiment. Its essence was that a cat was locked in a box with an infernal machine. The machine is connected through a relay to a quantum system, for example, a radioactively decaying substance. The decay probability is known and is 50%. The infernal machine works when the quantum state of the system changes (decay occurs) and the cat dies completely. If you leave the "Cat-box-infernal machine-quanta" system to itself for one hour and remember that the state of the quantum system is described in terms of probability, then it becomes clear that it's probably impossible to find out whether the cat is alive or not, at a given moment in time, just as it will not work out accurately to predict the fall of a coin on heads or tails in advance. The paradox is very simple: the wave function describing a quantum system mixes 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 the atomic nucleus. If we don't open the box, we don't know exactly how the cat is. Without making observations (read measurements) on the atomic nucleus, we can describe its state only by a superposition (mixing) of two states: a decayed and non-decayed nucleus. A nuclear-addicted cat is both alive and dead at the same time. The question is this: when does a system cease to exist as a mixture of two states and chooses one concrete 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 takes place, which is also a measurement (the box opens). That is, the very fact of measurement changes the 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 that accompany it change the reality around us. Personally, this fact makes my 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 sharpness 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 (falling it to one of two probabilistic) states is greatly exaggerated.
Of course, when Professor Erwin conceived his cat-fraud back in 1935, it was a clever way to show the imperfection of quantum mechanics. Indeed, a cat cannot be alive and dead at the same time. As a result, one of the interpretations of the experiment was the obvious contradiction between the laws of the macro-world (for example, the second law of thermodynamics - a cat is either alive or dead) and the micro-world (a cat is alive and dead at the same time).
The above is applied in practice: in quantum computing and in quantum cryptography. A fiber-optic cable sends a light signal that is in a superposition of two states. 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. Having carried out statistical tests of light at the receiving end of the cable, it will be possible to find out whether the light is in a superposition of states or whether it has already been observed and transmitted to another point. This makes it possible to create means of communication that exclude imperceptible signal interception and eavesdropping.
Another most recent interpretation of Schrödinger's thought experiment is the story of Sheldon Cooper, the hero of the Big Bang Theory series, which he spoke to the less educated neighbor Penny. The point of Sheldon's story is that the concept of Schrödinger's cat can be applied to 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. Until then, relationships are both good and bad.
