Quantum theory. Fundamentals of quantum physics: concepts, laws, connection with consciousness
If you suddenly realized that you have forgotten the basics and postulates of quantum mechanics or don’t even know what kind of mechanics it is, then it’s time to refresh your memory of this information. After all, no one knows when quantum mechanics may be useful in life.
It’s in vain that you grin and sneer, thinking that you will never have to deal with this subject in your life. After all, quantum mechanics can be useful to almost every person, even those infinitely far from it. For example, you have insomnia. For quantum mechanics this is not a problem! Read the textbook before going to bed - and you will fall into a deep sleep on the third page. Or you can call your cool rock band that. Why not?
Jokes aside, let's start a serious quantum conversation.
Where to begin? Of course, starting with what quantum is.
Quantum
Quantum (from the Latin quantum - “how much”) is an indivisible portion of some physical quantity. For example, they say - a quantum of light, a quantum of energy or a quantum of field.
What does it mean? This means that it simply cannot be less. When they say that some quantity is quantized, they understand that given value takes on a number of specific, discrete values. Thus, the energy of an electron in an atom is quantized, light is distributed in “portions”, that is, in quanta.
The term "quantum" itself has many uses. Quantum of light ( electromagnetic field) is a photon. By analogy, quanta are particles or quasiparticles corresponding to other interaction fields. Here we can recall the famous Higgs boson, which is a quantum of the Higgs field. But we are not going into these jungles yet.
Quantum mechanics for dummies How can mechanics be quantum?
As you have already noticed, in our conversation we mentioned particles many times. You may be accustomed to the fact that light is a wave that simply propagates at speed With . But if you look at everything from the point of view quantum world, that is, the world of particles, everything changes beyond recognition.
Quantum mechanics is a section theoretical physics, a component of quantum theory that describes physical phenomena at the most elementary level - the level of particles.
The effect of such phenomena is comparable in magnitude to Planck's constant, and Newton's classical mechanics and electrodynamics turned out to be completely unsuitable for describing them. For example, according to classical theory An electron, rotating at high speed around the nucleus, must radiate energy and eventually fall onto the nucleus. This, as we know, does not happen. That is why quantum mechanics was invented - the discovered phenomena had to be explained somehow, and it turned out to be precisely the theory within which the explanation was the most acceptable, and all experimental data “converged”.
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A little history
The birth of quantum theory occurred in 1900, when Max Planck spoke at a meeting of the German Physical Society. What did Planck say then? And the fact that the radiation of atoms is discrete, and the smallest portion of the energy of this radiation is equal to
Where h is Planck's constant, nu is the frequency.
Then Albert Einstein, introducing the concept of “quantum of light”, used Planck’s hypothesis to explain the photoelectric effect. Niels Bohr postulated the existence of stationary energy levels in the atom, and Louis de Broglie developed the idea of wave-particle duality, that is, that a particle (corpuscle) also has wave properties. Schrödinger and Heisenberg joined the cause, and in 1925 the first formulation of quantum mechanics was published. Actually, quantum mechanics is far from a complete theory; it is actively developing at the present time. It should also be recognized that quantum mechanics, with its assumptions, does not have the ability to explain all the questions it faces. It is quite possible that it will be replaced by a more advanced theory.
During the transition from the quantum world to the world of things familiar to us, the laws of quantum mechanics are naturally transformed into the laws of classical mechanics. We can say that classical mechanics is a special case of quantum mechanics, when the action takes place in our familiar and familiar macroworld. Here bodies move calmly in non-inertial frames of reference at a speed much lower than the speed of light, and in general everything around is calm and clear. If you want to know the position of a body in a coordinate system, no problem; if you want to measure the impulse, you’re welcome.
Quantum mechanics has a completely different approach to the issue. It contains the measurement results physical quantities are probabilistic in nature. This means that when a certain value changes, several results are possible, each of which has a certain probability. Let's give an example: a coin is spinning on the table. While it is spinning, it is not in any specific state (heads-tails), but only has the probability of ending up in one of these states.
Here we are gradually approaching Schrödinger equation And Heisenberg uncertainty principle.
According to legend, Erwin Schrödinger, in 1926, speaking at a scientific seminar on the topic of wave-particle duality, was criticized by a certain senior scientist. Refusing to listen to his elders, after this incident Schrödinger actively began developing the wave equation to describe particles within the framework of quantum mechanics. And he did it brilliantly! The Schrödinger equation (the basic equation of quantum mechanics) is:
This type equations - the one-dimensional stationary Schrödinger equation - the simplest.
Here x is the distance or coordinate of the particle, m is the mass of the particle, E and U are its total and potential energies, respectively. The solution to this equation is the wave function (psi)
The wave function is another fundamental concept in quantum mechanics. So, any quantum system that is in some state has a wave function that describes this state.
For example, when solving the one-dimensional stationary Schrödinger equation, the wave function describes the position of the particle in space. More precisely, the probability of finding a particle at a certain point in space. In other words, Schrödinger showed that probability can be described by a wave equation! Agree, we should have thought of this before!
But why? Why do we have to deal with these incomprehensible probabilities and wave functions, when, it would seem, there is nothing simpler than just taking and measuring the distance to a particle or its speed.
Everything is very simple! Indeed, in the macrocosm this is indeed the case - we measure distances with a certain accuracy with a tape measure, and the measurement error is determined by the characteristics of the device. On the other hand, we can almost accurately determine by eye the distance to an object, for example, to a table. In any case, we accurately differentiate its position in the room relative to us and other objects. In the world of particles, the situation is fundamentally different - we simply physically do not have measurement tools to accurately measure the required quantities. After all, the measuring instrument comes into direct contact with the object being measured, and in our case, both the object and the instrument are particles. It is this imperfection, the fundamental impossibility of taking into account all the factors acting on the particle, as well as the very fact of changing the state of the system under the influence of measurement, that underlies the Heisenberg uncertainty principle.
Let us give its simplest formulation. Let's imagine that there is a certain particle, and we want to know its speed and coordinate.
In this context, the Heisenberg Uncertainty Principle states that it is impossible to accurately measure the position and velocity of a particle at the same time. . Mathematically it is written like this:
Here delta x is the error in determining the coordinate, delta v is the error in determining the speed. Let us emphasize that this principle says that the more accurately we determine the coordinate, the less accurately we will know the speed. And if we determine the speed, we will not have the slightest idea of where the particle is.
There are many jokes and anecdotes on the topic of the uncertainty principle. Here is one of them:
A policeman stops a quantum physicist.
- Sir, do you know how fast you were moving?
- No, but I know exactly where I am.
And, of course, we remind you! If, for some reason, solving the Schrödinger equation for a particle in a potential well keeps you awake, turn to professionals who were raised with quantum mechanics on their lips!
Classical physics, which existed before the invention of quantum mechanics, describes nature on an ordinary (macroscopic) scale. Most theories in classical physics can be derived as approximations operating on scales that are familiar to us. Quantum physics (also known as quantum mechanics) differs from classical science in that the energy, momentum, angular momentum and other quantities of a coupled system are limited to discrete values (quantization). Objects have special characteristics as both particles and waves (wave particle duality). Also in this science there are limits to the accuracy with which quantities can be measured (the uncertainty principle).
It can be said that after the emergence quantum physics A kind of revolution took place in the exact sciences, which made it possible to reconsider and analyze all the old laws that were previously considered immutable truths. Is it good or bad? Perhaps it’s good, because true science should never stand still.
However, the “quantum revolution” was a kind of blow for old-school physicists, who had to come to terms with the fact that what they believed in before turned out to be just a set of erroneous and archaic theories that needed urgent revision and adaptation to new reality. Most physicists enthusiastically accepted these new ideas about a well-known science, making their contribution to its study, development and implementation. Today, quantum physics sets the dynamics for all science as a whole. Advanced experimental projects (like the Large Hadron Collider) arose precisely thanks to her.
Opening
What can be said about the foundations of quantum physics? It gradually emerged from various theories, intended to explain phenomena that could not be reconciled with classical physics, such as Max Planck's solution in 1900 and his approach to the radiation problem of many scientific problems, and the correspondence between energy and frequency in Albert Einstein's 1905 paper that explained photoelectric effects . The early theory of quantum physics was thoroughly revised in the mid-1920s by Werner Heisenberg, Max Born and others. The modern theory is formulated in various specially developed mathematical concepts. In one of them, the arithmetic function (or wave function) gives us comprehensive information about the amplitude of the probability of the location of the pulse.
Scientific research The wave essence of light began more than 200 years ago, when the great and recognized scientists of that time proposed, developed and proved the theory of light based on their own experimental observations. They called it wave.
In 1803, the famous English scientist Thomas Young conducted his famous double experiment, as a result of which he wrote the famous work “On the Nature of Light and Color,” which played a huge role in the formation modern ideas about these phenomena familiar to us all. This experiment played vital role in general acceptance of this theory.
Such experiments are often described in various books, for example, “Fundamentals of Quantum Physics for Dummies.” Modern experiments with the acceleration of elementary particles, for example, the search for the Higgs boson in the Large Hadron Collider (abbreviated as LHC), are carried out precisely in order to find practical confirmation of many purely theoretical quantum theories.
Story
In 1838, Michael Faraday discovered cathode rays to the delight of the whole world. These sensational studies were followed by a statement about the problem of so-called “black body” radiation (1859), made by Gustav Kirchhoff, as well as the famous assumption of Ludwig Boltzmann that the energy states of any physical system can also be discrete (1877 ). Only then did the quantum hypothesis appear, developed by Max Planck (1900). It is considered one of the foundations of quantum physics. The bold idea that energy can be both emitted and absorbed in discrete "quanta" (or packets of energy) matches exactly the observed patterns of black body radiation.
Albert Einstein, famous throughout the world, made a great contribution to quantum physics. Impressed by quantum theories, he developed his own. General theory relativity - that's what it's called. Discoveries in quantum physics also influenced the development of the special theory of relativity. Many scientists in the first half of the last century began to study this science at the suggestion of Einstein. At that time she was advanced, everyone liked her, everyone was interested in her. Not surprising, since it covered so many “holes” in the classical physical science(although she also created new ones), offered a scientific basis for time travel, telekinesis, telepathy and parallel worlds.
The role of the observer
Any event or state depends directly on the observer. This is usually how the basics of quantum physics are briefly explained to people far from the exact sciences. However, in reality everything is much more complicated.
This fits perfectly with many occult and religious traditions, which from time immemorial have insisted on the ability of people to influence the events around them. In a way, this is also the basis for a scientific explanation of extrasensory perception, because now the statement that a person (observer) is able to influence physical events with the power of thought does not seem absurd.
Each eigenstate of an observed event or object corresponds to an eigenvector of the observer. If the spectrum of the operator (observer) is discrete, the observed object can only reach discrete eigenvalues. That is, the object of observation, as well as its characteristics, is completely determined by this very operator.
Unlike the generally accepted classical mechanics(or physicists), simultaneous predictions of conjugate variables such as position and momentum cannot be made here. For example, electrons may (with a certain probability) be located approximately in a certain region of space, but their mathematically precise location is actually unknown.
Constant probability density contours, often called "clouds", can be drawn around the nucleus of an atom to conceptualize where an electron is most likely to be located. The Heisenberg Uncertainty Principle proves the inability to accurately locate a particle given its conjugate momentum. Some models in this theory are of a purely abstract computational nature and do not imply practical significance. However, they are often used to calculate complex interactions at the level of other subtle matters. In addition, this branch of physics allowed scientists to assume the possibility of the real existence of many worlds. Perhaps we will be able to see them soon.
Wave functions
The laws of quantum physics are very extensive and varied. They overlap with the idea of wave functions. Some special ones create a spread of probabilities that is inherently constant or independent of time, for example, when in a stationary position of energy time seems to disappear in relation to the wave function. This is one of the effects of quantum physics, which is fundamental to it. An interesting fact is that the phenomenon of time has been radically revised in this unusual science.
Perturbation theory
However, there are several reliable ways to develop the solutions needed to work with the formulas and theories in quantum physics. One such method, commonly known as “perturbation theory,” uses an analytical result for an elementary quantum mechanical model. It was created to gain results from experiments to develop an even more complex model that is related to a simpler model. This is how recursion turns out.
This approach is especially important in quantum chaos theory, which is extremely popular for treating various events in microscopic reality.
Rules and laws
The rules of quantum mechanics are fundamental. They argue that the deployment space of a system is absolutely fundamental (it has scalar product). Another statement is that the effects observed by this system are at the same time unique operators influencing vectors in this very environment. However, they do not tell us which Hilbert space or which operators exist in this moment. They can be chosen appropriately to obtain a quantitative description of the quantum system.
Meaning and influence
Since the inception of this unusual science, many counter-intuitive aspects and results of the study of quantum mechanics have provoked much philosophical debate and many interpretations. Even fundamental questions, such as the rules for calculating various amplitudes and probability distributions, deserve respect from the public and many leading scientists.
For example, he once sadly noted that he was not at all sure that any scientist even understood quantum mechanics. According to Steven Weinberg, at the moment there is no interpretation of quantum mechanics that would suit everyone. This suggests that scientists have created a “monster” whose existence they themselves are unable to fully understand and explain. However, this does not in any way harm the relevance and popularity of this science, but attracts young specialists to it who want to solve truly complex and incomprehensible problems.
In addition, quantum mechanics has forced us to completely reconsider the objective physical laws of the Universe, which is good news.
Copenhagen interpretation
According to this interpretation, the standard definition of causality that we know from classical physics is no longer needed. According to quantum theories, causality in our usual understanding does not exist at all. All physical phenomena are explained in them from the point of view of the interaction of the smallest elementary particles at the subatomic level. This area, despite its apparent improbability, is extremely promising.
Quantum psychology
What can be said about the relationship between quantum physics and human consciousness? This is beautifully written about in a book written by Robert Anton Wilson in 1990 called Quantum Psychology.
According to the theory outlined in the book, all processes occurring in our brain are determined by the laws described in this article. That is, this is a kind of attempt to adapt the theory of quantum physics to psychology. This theory is considered parascientific and is not recognized by the academic community.
Wilson's book is notable for the fact that he provides a set of various techniques and practitioners who, to one degree or another, prove his hypothesis. One way or another, the reader must decide for himself whether he believes or not the validity of such attempts to apply mathematical and physical models to the humanities.
Wilson's book was seen by some as an attempt to justify mystical thinking and tie it to scientifically proven newfangled physics formulations. This very non-trivial and brilliant work has remained in demand for more than 100 years. The book is published, translated and read all over the world. Who knows, perhaps with the development of quantum mechanics, the attitude of the scientific community towards quantum psychology will change.
Conclusion
Thanks to this remarkable theory, which soon became a separate science, we were able to explore the surrounding reality at the level of subatomic particles. This is the smallest level of all possible, completely inaccessible to our perception. What physicists previously knew about our world needs urgent revision. Absolutely everyone agrees with this. It became obvious that different particles can interact with each other at completely unimaginable distances, which we can only measure using complex mathematical formulas.
In addition, quantum mechanics (and quantum physics) have proven the possibility of multiple parallel realities, time travel, and other things that throughout history were considered only the province of science fiction. This is undoubtedly a huge contribution not only to science, but also to the future of humanity.
For lovers of the scientific picture of the world, this science can be both a friend and an enemy. The fact is that quantum theory reveals ample opportunities for various speculations on a parascientific topic, as has already been shown in the example of one of the alternative psychological theories. Some modern occultists, esotericists and supporters of alternative religious and spiritual movements (most often psychocults) turn to the theoretical constructs of this science in order to substantiate the rationality and truth of their mystical theories, beliefs and practices.
This is an unprecedented case when simple speculations of theorists and abstract mathematical formulas led to a real scientific revolution and created new science, which crossed out everything that was previously known. To some extent, quantum physics refuted the laws of Aristotelian logic, because it showed that when choosing “either-or” there is one more (and possibly several) alternative option.
In this article we will give useful tips on studying quantum physics for dummies. Let us answer what should be the approach in learning quantum physics for beginners.
The quantum physics- This is a rather complex discipline that not everyone can easily master. Nevertheless, physics as a subject is interesting and useful, which is why quantum physics (http://www.cyberforum.ru/quantum-physics/) finds its fans who are ready to study it and ultimately get practical benefits. To make it easier to learn the material, you need to start from the very beginning, that is, with the simplest quantum physics textbooks for beginners. This will allow you to get a good basis for knowledge, and at the same time well structure your knowledge in your head.
You need to start self-studying with good literature. It is literature that is the decisive factor in the process of acquiring knowledge and ensures its quality. Quantum mechanics is of particular interest, and many begin their studies with it. Everyone should know physics, because it is the science of life, which explains many processes and makes them understandable to others.
Please note that when you start studying quantum physics, you must have knowledge of mathematics and physics, as without them you simply will not cope. It will be good if you have the opportunity to contact your teacher to find answers to your questions. If this is not possible, you can try to clarify the situation on specialized forums. Forums can also be very useful in learning.
When you decide on the choice of a textbook, you must be prepared for the fact that it is quite complex and you will have to not just read it, but delve into everything that is written in it. So that at the end of the training you do not have the idea that this is all unnecessary knowledge for anyone, try to connect theory with practice each time. It is also important to determine in advance the purpose for which you began to learn quantum physics, in order to prevent the emergence of thoughts about the uselessness of the knowledge acquired. People fall into two categories: people who think quantum physics is an interesting and useful subject and those who don't. Choose for yourself which category you belong to and accordingly determine whether quantum physics has a place in your life or not. You can always remain at the beginner level in studying quantum physics, or you can achieve real success, everything is in your hands.
First of all, choose really interesting and quality materials in physics. You can find some of them using the links below.
And that's all for now! Study quantum physics in an interesting way and don’t be a dummie!
Hello dear readers. If you don't want to lag behind life, be truly happy and healthy person, you should know about the secrets of quantum modern physics, at least have a little idea to what depths of the universe scientists have dug today. You don’t have time to go into deep scientific details, but want to comprehend only the essence, but see the beauty of the unknown world, then this article: quantum physics for regular teapots or you can say for housewives just for you. I will try to explain what quantum physics is, but in simple words, show clearly.
“What is the connection between happiness, health and quantum physics?” you ask.
The fact is that it helps answer many unclear questions related to human consciousness and the influence of consciousness on the body. Unfortunately, medicine, based on classical physics, does not always help us to be healthy. But psychology cannot properly say how to find happiness.
Only a deeper knowledge of the world will help us understand how to truly cope with illness and where happiness lives. This knowledge is found in the deep layers of the Universe. Quantum physics comes to our aid. Soon you will know everything.
What quantum physics studies in simple words
Yes, quantum physics is indeed very difficult to understand because it studies the laws of the microworld. That is, the world is in its deeper layers, at very short distances, where it is very difficult for a person to see.
And the world, it turns out, behaves there very strangely, mysteriously and incomprehensibly, not as we are used to.
Hence all the complexity and misunderstanding of quantum physics.
But after reading this article, you will expand the horizons of your knowledge and look at the world in a completely different way.
Brief history of quantum physics
It all started at the beginning of the 20th century, when Newtonian physics could not explain many things and scientists reached a dead end. Then Max Planck introduced the concept of quantum. Albert Einstein picked up this idea and proved that light does not travel continuously, but in portions - quanta (photons). Before this, it was believed that light had a wave nature.
But as it turned out later, any elementary particle, this is not only a quantum, that is, a solid particle, but also a wave. This is how wave-particle dualism appeared in quantum physics, the first paradox and the beginning of discoveries of mysterious phenomena of the microworld.
The most interesting paradoxes began when the famous double-slit experiment was carried out, after which there were many more mysteries. We can say that quantum physics began with him. Let's look at it.
Double slit experiment in quantum physics
Imagine a plate with two slits in the form of vertical stripes. We will place a screen behind this plate. If we shine light on the plate, we will see an interference pattern on the screen. That is, alternating dark and bright vertical stripes. Interference is the result of the wave behavior of something, in our case light.
If you pass a wave of water through two holes located next to each other, you will understand what interference is. That is, the light turns out to be of a wave nature. But as physics, or rather Einstein, has proven, it is propagated by photon particles. Already a paradox. But that’s okay, wave-particle duality will no longer surprise us. Quantum physics tells us that light behaves like a wave but is made up of photons. But miracles are just beginning.
Let's put a gun in front of the plate with two slits that will emit electrons rather than light. Let's start shooting electrons. What will we see on the screen behind the plate?
Electrons are particles, which means that a flow of electrons passing through two slits should leave only two stripes on the screen, two traces opposite the slits. Imagine pebbles flying through two slits and hitting the screen?
But what do we actually see? The same interference pattern. What is the conclusion: electrons travel in waves. So electrons are waves. But this is an elementary particle. Again, wave-particle dualism in physics.
But we can assume that at a deeper level, the electron is a particle, and when these particles come together, they begin to behave like waves. For example, a sea wave is a wave, but it consists of drops of water, and at a smaller level of molecules, and then of atoms. Okay, the logic is solid.
Then let's shoot from a gun not with a stream of electrons, but release electrons separately, after a certain period of time. As if we were not passing through the cracks sea wave, and would spit out individual drops from a child’s water pistol.
It is quite logical that in this case different drops of water would fall into different cracks. On the screen behind the plate one would see not an interference pattern from the wave, but two clear stripes from the impact opposite each slit. We will see the same thing: if you throw small stones, they, flying through two slits, would leave a mark, like a shadow from two holes. Let's now shoot individual electrons to see these two streaks on the screen from the electron impacts. They released one, waited, the second, waited, and so on. Quantum physics scientists were able to do such an experiment.
But horror. Instead of these two bands, the same interference alternations of several bands are obtained. How so? This could happen if an electron were flying through two slits at the same time, and behind the plate, like a wave, it would collide with itself and interfere. But this cannot happen, because a particle cannot be in two places at the same time. It either flies through the first gap or through the second.
This is where the truly fantastic things of quantum physics begin.
Superposition in quantum physics
With a deeper analysis, scientists find out that any elementary quantum particle or the same light (photon) can actually be in several places at the same time. And these are not miracles, but real facts microworld. Quantum physics says so. That's why, when we shoot a single particle from a cannon, we see the result of interference. Behind the plate, the electron collides with itself and creates an interference pattern.
The objects of the macrocosm that are common to us are always in one place and have one state. For example, you are now sitting on a chair, weigh, say, 50 kg, and have a heart rate of 60 beats per minute. Of course, these readings will change, but they will change after some time. After all, you cannot be at home and at work at the same time, weigh 50 and 100 kg. All this is understandable, it is common sense.
In the physics of the microworld, everything is different.
Quantum mechanics states, and this has already been confirmed experimentally, that any elementary particle can simultaneously be not only in several points in space, but also have several states at the same time, for example, spin.
All this boggles the mind, undermines the usual understanding of the world, the old laws of physics, turns thinking upside down, one can safely say drives you crazy.
This is how we come to understand the term “superposition” in quantum mechanics.
Superposition means that an object of the microworld can simultaneously be in different points of space, and also have several states at the same time. And this is normal for elementary particles. This is the law of the microworld, no matter how strange and fantastic it may seem.
You are surprised, but these are just the beginnings, the most inexplicable miracles, mysteries and paradoxes of quantum physics are yet to come.
Wave function collapse in physics in simple words
Then the scientists decided to find out and see more precisely whether the electron actually passes through both slits. All of a sudden it passes through one slit and then somehow splits and creates an interference pattern as it passes through it. Well, you never know. That is, you need to place some kind of device near the slit that would accurately record the passage of an electron through it. No sooner said than done. Of course, this is difficult to do; you need not a device, but something else to see the passage of an electron. But scientists did it.
But in the end, the result stunned everyone.
As soon as we begin to look through which slit the electron passes, it begins to behave not like a wave, not like a strange substance that is simultaneously located in different points of space, but like an ordinary particle. That is, the quantum begins to exhibit specific properties: it is located in only one place, passes through one slit, and has one spin value. It is not an interference pattern that appears on the screen, but a simple trace opposite the slit.
But how is this possible? It’s as if the electron is joking, playing with us. At first it behaves like a wave, and then, after we decided to watch it pass through a slit, it exhibits the properties of a solid particle and passes through only one slit. But this is how it is in the microcosm. These are the laws of quantum physics.
Scientists have seen another mysterious property elementary particles. This is how the concepts of uncertainty and wave function collapse appeared in quantum physics.
When an electron flies to the slit, it is in an indeterminate state or, as we said above, in a superposition. That is, it behaves like a wave, is simultaneously in different points of space, and has two spin values at once (spin has only two values). If we didn’t touch it, didn’t try to look at it, didn’t find out where exactly it was, didn’t measure the value of its spin, it would have flown like a wave through two slits at the same time, which means it would have created an interference pattern. Quantum physics describes its trajectory and parameters using the wave function.
After we have made a measurement (and you can measure a particle of the microworld only by interacting with it, for example, by colliding another particle with it), then the collapse of the wave function occurs.
That is, now the electron is located exactly in one place in space and has one spin value.
You can say an elementary particle is like a ghost, it seems to exist, but at the same time it is not in one place, and can, with a certain probability, end up in any place within the description of the wave function. But as soon as we begin to contact it, it turns from a ghostly object into a real tangible substance that behaves like ordinary objects of the classical world that are familiar to us.
“This is fantastic,” you say. Of course, but the wonders of quantum physics are just beginning. The most incredible is yet to come. But let's take a little break from the abundance of information and return to quantum adventures another time, in another article. In the meantime, reflect on what you learned today. What can such miracles lead to? After all, they surround us, this is a property of our world, albeit on a deeper level. Do we still think that we live in a boring world? But we will draw conclusions later.
I tried to talk about the basics of quantum physics briefly and clearly.
But if you don’t understand something, then watch this cartoon about quantum physics, about the double-slit experiment, everything is also explained there in clear, simple language.
Cartoon about quantum physics:
Or you can watch this video, everything will fall into place, quantum physics is very interesting.
Video about quantum physics:
And how did you not know about this before?
Modern discoveries in quantum physics are changing our familiar material world.
- Translation
According to Owen Maroney, a physicist at the University of Oxford, since the advent of quantum theory in the 1900s, everyone has been talking about the strangeness of the theory. How it allows particles and atoms to move in multiple directions at the same time, or rotate clockwise and counterclockwise at the same time. But words can't prove anything. “If we tell the public that quantum theory is very strange, we need to test this statement experimentally,” Maroney says. “Otherwise, we’re not doing science, but talking about all sorts of squiggles on the board.”
This is what gave Maroney and his colleagues the idea to develop a new series of experiments to uncover the essence of the wave function - the mysterious entity underlying quantum oddities. On paper, the wave function is simply a mathematical object, denoted by the letter psi (Ψ) (one of those squiggles), and is used to describe the quantum behavior of particles. Depending on the experiment, the wave function allows scientists to calculate the probability of seeing an electron in a particular location, or the chances that its spin is oriented up or down. But the math doesn't tell you what a wave function actually is. Is it something physical? Or simply a computational tool to deal with the observer's ignorance of the real world?
The tests used to answer the question are very subtle and have yet to produce a definitive answer. But researchers are optimistic that the end is near. And they will finally be able to answer the questions that have tormented everyone for decades. Can a particle really be in many places at the same time? Is the Universe constantly dividing into Parallel Worlds, in each of which ours exists alternative version? Does something called “objective reality” even exist?
“Everyone has questions like these sooner or later,” says Alessandro Fedricci, a physicist at the University of Queensland (Australia). “What is actually real?”
Disputes about the essence of reality began when physicists discovered that a wave and a particle are just two sides of the same coin. Classic example– a double-slit experiment, where individual electrons are shot into a barrier that has two slits: the electron behaves as if it is passing through two slits at the same time, creating a striped interference pattern on the other side of it. In 1926, Austrian physicist Erwin Schrödinger came up with a wave function to describe this behavior and derived an equation that could be calculated for any situation. But neither he nor anyone else could say anything about the nature of this function.
Grace in Ignorance
From a practical point of view, its nature is not important. The Copenhagen interpretation of quantum theory, created in the 1920s by Niels Bohr and Werner Heisenberg, uses the wave function simply as a tool for predicting the results of observations, without having to think about what is happening in reality. “Physicists cannot be blamed for this “shut up and count” behavior, since it has led to significant breakthroughs in nuclear and atomic physics, physics solid and particle physics,” says Jean Bricmont, a statistical physicist at the Catholic University of Belgium. “So people are advised not to worry about fundamental issues.”
But some are still worried. By the 1930s, Einstein had rejected the Copenhagen interpretation, not least because it allowed two particles to entangle their wave functions, leading to a situation in which measurements of one could instantly give the state of the other, even if they were separated by enormous distances. distances. In order not to come to terms with this “frightening interaction at a distance,” Einstein preferred to believe that the wave functions of particles were incomplete. He said that it is possible that particles have some hidden variables that determine the result of a measurement that were not noticed by quantum theory.
Experiments have since demonstrated the functionality of fearful interaction at a distance, which rejects the concept of hidden variables. but this did not stop other physicists from interpreting them in their own way. These interpretations fall into two camps. Some agree with Einstein that the wave function reflects our ignorance. These are what philosophers call psi-epistemic models. And others view the wave function as a real thing - psi-ontic models.
To understand the difference, let's imagine Schrödinger's thought experiment, which he described in a 1935 letter to Einstein. The cat is in a steel box. The box contains a sample of radioactive material that has a 50% chance of releasing a decay product in one hour, and a machine that will poison the cat if this product is detected. Since radioactive decay is a quantum-level event, Schrödinger writes, the rules of quantum theory say that at the end of the hour the wave function of the inside of the box must be a mixture of a dead and a living cat.
“Roughly speaking,” Fedricci puts it mildly, “in the psi-epistemic model, the cat in the box is either alive or dead, and we just don’t know it because the box is closed.” And in most psionic models there is agreement with the Copenhagen interpretation: until the observer opens the box, the cat will be both alive and dead.
But here the dispute reaches a dead end. Which interpretation is true? This question is difficult to answer experimentally because the differences between the models are very subtle. They are essentially supposed to predict the same quantum phenomenon as the very successful Copenhagen interpretation. Andrew White, a physicist at the University of Queensland, says that during his 20-year career in quantum technology, "this problem was like a huge smooth mountain with no ledges that you couldn't approach."
Everything changed in 2011, with the publication of the quantum measurement theorem, which seemed to eliminate the “wave function as ignorance” approach. But upon closer examination it turned out that this theorem leaves enough room for their maneuver. However, it has inspired physicists to think seriously about ways to resolve the dispute by testing the reality of the wave function. Maroney had already designed an experiment that worked in principle, and he and his colleagues soon found a way to make it work in practice. The experiment was carried out last year by Fedrici, White and others.
To understand the idea of the test, imagine two decks of cards. One has only reds, the other only aces. “You are given a card and asked to identify which deck it comes from,” says Martin Ringbauer, a physicist at the same university. If it's a red ace, "there's going to be a crossover and you can't tell for sure." But if you know how many cards are in each deck, you can calculate how often this ambiguous situation will arise.
Physics in danger
The same ambiguity happens in quantum systems. It is not always possible to find out, for example, how polarized a photon is by one measurement. “In real life, it's easy to distinguish between west and a direction just south of west, but in quantum systems it's not so easy,” White says. According to the standard Copenhagen interpretation, there is no point in asking about polarization, since the question has no answer - until one more measurement determines the answer exactly. But according to the wavefunction-as-ignorance model, the question makes sense—it's just that the experiment, like the one with decks of cards, lacks information. As with maps, it is possible to predict how many ambiguous situations can be explained by such ignorance, and compare them with the large number of ambiguous situations resolved by standard theory.
This is exactly what Fedrici and his team tested. The team measured polarization and other properties in the photon beam, and found levels of intersection that could not be explained by "ignorance" models. The result supports an alternative theory - if objective reality exists, then the wave function exists. “It’s impressive that the team was able to solve this difficult task such a simple experiment,” says Andrea Alberti, a physicist at the University of Bonn (Germany).
The conclusion is not yet set in stone: since the detectors caught only a fifth of the photons used in the test, we have to assume that the lost photons behaved in the same way. This is a strong assumption, and the team is now working to reduce losses and produce a more definitive result. Meanwhile, Maroney's team at Oxford is working with the University of New South Wales in Australia to replicate the experiment with ions that are easier to track. "In the next six months we will have a conclusive version of this experiment," Maroney says.
But even if they are successful and the “wave function as reality” models win, then these models also have different variants. Experimenters will have to choose one of them.
One of the earliest interpretations was made in the 1920s by the Frenchman Louis de Broglie, and expanded in the 1950s by the American David Bohm. According to Broglie-Bohm models, particles have a specific location and properties, but they are driven by a certain “pilot wave”, which is defined as a wave function. This explains the two-slit experiment, since the pilot wave can pass through both slits and produce an interference pattern, although the electron itself, attracted by it, passes through only one of the two slits.
In 2005, this model received unexpected support. Physicists Emmanuel Fort, now at the Langevin Institute in Paris, and Yves Caudier of Paris Diderot University gave students what they thought was a simple problem: set up an experiment in which drops of oil falling on a tray would merge due to the vibrations of the tray. To everyone's surprise, waves began to form around the droplets as the tray vibrated at a certain frequency. “The droplets began to move independently on their own waves,” says Fort. “It was a dual object - a particle drawn by a wave.”
Forth and Caudier have since shown that such waves can conduct their particles in a double-slit experiment exactly as pilot wave theory predicts, and can reproduce other quantum effects. But this does not prove the existence of pilot waves in the quantum world. “We were told that such effects were impossible in classical physics,” says Fort. “And here we showed what is possible.”
Another set of reality-based models, developed in the 1980s, attempts to explain the vast differences in properties between large and small objects. “Why can electrons and atoms be in two places at once, but tables, chairs, people and cats cannot,” says Angelo Basi, a physicist at the University of Trieste (Italy). Known as “collapse models,” these theories say that the wave functions of individual particles are real, but can lose their quantum properties and force the particle into a specific position in space. The models are designed so that the chances of such a collapse are extremely small for an individual particle, so that quantum effects dominate at the atomic level. But the probability of collapse increases rapidly as particles combine, and macroscopic objects completely lose their quantum properties and behave according to the laws of classical physics.
One way to test this is to look for quantum effects in large objects. If standard quantum theory is correct, then there is no limit on size. And physicists have already conducted a double-slit experiment using large molecules. But if collapse models are correct, then quantum effects will not be visible above a certain mass. Various groups They plan to search for this mass using cold atoms, molecules, metal clusters and nanoparticles. They hope to discover results in the next ten years. "What's cool with these experiments is that we'll be challenging quantum theory accurate tests where it hasn’t been tested yet,” Maroney says.
Parallel Worlds
One "wave function as reality" model is already known and loved by science fiction writers. This is a many-worlds interpretation developed in the 1950s by Hugh Everett, who was a student at Princeton University in New Jersey at the time. In this model, the wave function so strongly determines the development of reality that with each quantum measurement the Universe splits into parallel worlds. In other words, when we open a box with a cat, we give birth to two Universes - one with a dead cat, and the other with a living one.It is difficult to separate this interpretation from standard quantum theory because their predictions are the same. But last year, Howard Wiseman of Griffith University in Brisbane and his colleagues proposed a testable model of the multiverse. There is no wave function in their model - particles obey classical physics, Newton's laws. And the strange effects of the quantum world appear because there are repulsive forces between particles and their clones in parallel universes. “The repulsive force between them creates waves that spread throughout the parallel worlds,” says Wiseman.
Using a computer simulation in which 41 universes interacted, they showed that the model roughly reproduced several quantum effects, including particle trajectories in the double-slit experiment. As the number of worlds increases, the interference pattern tends to the real one. Since the theory's predictions vary depending on the number of worlds, Wiseman says, it is possible to test whether the multiverse model is correct—that is, that there is no wave function and that reality operates according to classical laws.
Since the wave function is not needed in this model, it will remain viable even if future experiments rule out the "ignorance" models. Besides it, other models will survive, for example, the Copenhagen interpretation, which argue that no objective reality, but there are only calculations.
But then, White says, this question will become the object of study. And while no one knows how to do this yet, “what would be really interesting is to develop a test that tests whether we even have an objective reality.”