The Quantum Theory of Shah Society a. Is quantum theory a way of describing reality or our knowledge of it? Other books on similar topics
5.9. Relativistic quantum physics. The world of antiparticles. quantum field theory
Quantum mechanics, which in the first works of Bohr, Schrödinger, Heisenberg and other scientists was mainly the theory of atomic spectra, received intensive development in a short time and was generalized to a theory describing the behavior of micro-objects in the microcosm. Physicists began to divide the world around us into three levels: mega-, macro- and microworld. This became possible thanks to the synthesis of quantum mechanics and the special theory of relativity, thanks to the creation of relativistic quantum mechanics.
In 1927, the English physicist Paul Dirac, considering the Schrödinger equation, drew attention to its non-relativistic character. At the same time, quantum mechanics describes the objects of the microworld, and although by 1927 only three of them were known: the electron, proton and photon (even the neutron was experimentally discovered only in 1932), it was clear that they were moving at speeds very close to the speed of light or equal to it, and a more adequate description of their behavior requires the application of the special theory of relativity. Dirac compiled an equation that described the motion of an electron, taking into account the laws of both quantum mechanics and Einstein's theory of relativity, and obtained a formula for the energy of an electron, which was satisfied by two solutions: one solution gave a known electron with positive energy, the other - an unknown electron twin, but with negative energy. This is how the idea of particles and their corresponding
antiparticles, about worlds and antiworlds. By the same time, quantum electrodynamics had been developed. Its essence lies in the fact that the field is no longer considered as a continuous continuous medium. Dirac applied the quantization rules to the theory of the electromagnetic field, as a result of which he obtained discrete values of the field. The discovery of antiparticles deepened the understanding of the field. It was believed that there is no electromagnetic field if there are no quanta of this field - photons. Therefore, there must be a void in this region of space. After all, the special theory of relativity “expelled” the ether from the theory, we can say that the point of view about vacuum, about emptiness, won. But is the vacuum empty? That is the question that arose again in connection with the discovery of Dirac. Now the facts are well known, proving that the vacuum is empty only on the average. A huge number of virtual particles and antiparticles are constantly born and disappear in it. Even if we measure the charge of an electron, then, as it turned out, the bare charge of an electron would be equal to infinity. We measure the charge of an electron in the “fur coat” of virtual particles surrounding it.
Actually, the idea of vacuum as a continuous activity of virtual particles contained in it is contained in the Heisenberg uncertainty principle. The Heisenberg uncertainty principle has, in addition to the above, also the following expression: 
According to this, quantum effects can temporarily violate the law of conservation of energy. For a short time, the energy taken as if "on loan" can be spent on the creation of short-lived particles that disappear when the "loan" of energy returns. These are virtual particles. Arising from "nothing", they again return to "nothing". So the vacuum in physics turns out to be not empty, but is a sea of bursts that are born and immediately extinguished.
Quantum field theory is the core of all modern physics, it is a general approach to all known types of interactions. One of its most important results is the idea of a vacuum, but no longer empty, but saturated with all kinds of fluctuations of all kinds of fields. Vacuum in quantum field theory is defined as the lowest energy state of quantum
shaped field, the energy of which is equal to zero only on the average. So vacuum is "Something" called "Nothing".
The relativistic quantum field theory, which began with the works of Dirac, Pauli, Heisenberg at the end of the 20s of our century, was continued in the works of Feynman, Tomonaga, Schwinger and other scientists, giving an ever more complete idea of the physical indecomposability of the world, of to individual elements. Here the principle of integrity is reflected when considering the interaction of micro-objects with a certain state of the physical vacuum. It is in this interaction that all elementary particles reveal their properties. Vacuum is considered as an object of the physical world, expressing just the moment of its physical indecomposability.
What is the fate of the concept of "vacuum" in modern physics of the XXI century? Why does our world consist predominantly of matter, while "antimatter" remained hidden from our view for a long time? We will try to answer these and other questions in a brief outline of the current state of elementary particle physics at the turn of the third millennium, given in the next chapter. Finishing the conversation about quantum physics, we note that its results have completely changed our ideas about the world, our approach to the structure of physical laws. As a result, a new type of scientific thinking has been developed, called non-classical, in which there is a place for chance, probability, integrity.
Questions for self-control
Write Planck's formula and explain its physical meaning.
What physical effects are experimental confirmation of Planck's hypothesis?
What is the de Broglie hypothesis? What is the de Broglie wavelength?
Describe the experiment with two slits and explain how you understand the wave-particle duality of micro-objects.
What new ideas about the world arise in relativistic quantum physics? Tell us about antiparticles and virtual particles.
What is the physical vacuum in quantum field theory?
Other books on similar topics:
| author | Book | Description | Year | Price | book type |
|---|---|---|---|---|---|
| Shakhov Anatoly Alekseevich | Monographic formulation from a unified methodological standpoint of the developed quantum concept of a complete theoretical substantiation of reality and generalization of modern achievements in various sciences in ... - @Sputnik+, @(format: 60x90/16, 80 pages) @ @ @ | 2017 | 260 | paper book | |
| Shakhov Anatoly Alekseevich | Monographic formulation from a unified methodological standpoint of the developed quantum concept of a complete theoretical substantiation of reality and generalization of modern achievements in various sciences in ... - @Sputnik +, @(format: 60x90/16, 134 pages) @ @ @ | 2017 | 333 | paper book | |
| V. A. Filin | In this book, the author applies quantum theory to describe the development of society, trying to analyze from a natural scientific point of view one of the most destructive forces - the bureaucratic system ... - @Librocom, @(format: 60x90/16, 56 pages) @Relata Refero @ @ | 2009 | 86 | paper book | |
| V. A. Filin | Quantum theory of social development. A new look at economic and political processes | In this book, the author applies quantum theory to describe the development of society, trying to analyze from a natural scientific point of view one of the most destructive forces - the bureaucratic system ... - @Librokom, @(format: 60x90/16, 80 pages) @Relata Refero @ @ | 2011 | 286 | paper book |
| Filin V.A. | Quantum theory of social development. A new look at economic and political processes | In this book, the author applies quantum theory to describe the development of society, trying to analyze from a natural scientific point of view one of the most destructive forces - the bureaucratic system ... - @URSS, @(format: 60x90/16, 80 pages) @Relata Refero @ @ | 2012 | 189 | paper book |
| V. A. Filin | Quantum theory of social development. A new look at economic and political processes | In this book, the author applies quantum theory to describe the development of society, trying to analyze from a natural scientific point of view one of the most destructive forces - the bureaucratic system ... - @Librokom, @(format: 60x90/16, 80 pages) @ @ @ | 2011 | 244 | paper book |
| Paul Parsons | Scientific theories in 30 seconds | Chaos theory, unification or theory of everything, theory of relativity, Schrödinger's cat and laws of motion? Surely you know what it is. I mean, you've heard about it, of course. But did you know… - @StorySide AB, @(format: 60x90/16, 56 pages) @30 seconds @ audiobook @ downloadable | 2009 | 189 | audiobook |
| George Musser | Nonlocality. A phenomenon that changes the concept of space and time, and its significance for black holes, the Big Bang and theories of everything | Reviews`Locality was one of the fundamental principles that determined the triumphant development of physics in the 20th century. However, the paradoxes and contradictions of local laws and quantum theory have led to… - @Alpina Non-fiction, @(format: 60x90/16, 370 pages) @ @ @ | 2018 | 332 | paper book |
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The demonstration that turned the great Isaac Newton's ideas about the nature of light upside down was incredibly simple. It "can be repeated with great ease wherever the sun shines," said the English physicist Thomas Young in November 1803 to members of the Royal Society in London, describing what is now called the double slit experiment. And Yang was not an enthusiastic youth. He came up with an elegant and elaborate, demonstrating the wave nature of light, and thereby disproved Newton's theory that light consists of corpuscles, that is, particles.
Quantum theory is much more complicated than this visualization.
But the birth of quantum physics in the early 1900s made it clear that light is made up of tiny, indivisible units—or quanta—of energy that we call photons. Whether done with single photons or even individual particles of matter such as electrons and neurons, Young's experiment is a puzzle that raises questions about the very nature of reality. Some have even used it to claim that the quantum world is influenced by human consciousness. But can a simple experiment really demonstrate this?
Can consciousness determine reality?
In modern quantum form, Young's experiment involves firing individual particles of light or matter through two slits or holes cut into an opaque barrier. On one side of the barrier is a screen that records the arrival of the particles (say, a photographic plate in the case of photons). Common sense leads us to expect that photons will pass through either one or the other slit and accumulate behind the corresponding passage.
Are our efforts to describe reality nothing more than a game of dice trying to predict the desired outcome? James Owen Weatherall, professor of logic and philosophy of science at the University of Irvine, reflected on the pages of Nautil.us about the mysteries of quantum physics, the problem of the quantum state and how it depends on our actions, knowledge and subjective perception of reality, and why, predicting different probabilities, we all turn out to be right.
Physicists are well aware of how to apply quantum theory - your phone and computer are proof of that. But knowing how to use something is far from fully understanding the world described by the theory, or even what the various mathematical tools that scientists use mean. One such mathematical tool, the status of which physicists have been arguing for a long time, is the "quantum state" ⓘ A quantum state is any possible state that a quantum system can be in. In this case, the "quantum state" should also be understood as all the potential probabilities of falling out of one or another value when playing "dice". — Approx. ed..
One of the most striking features of quantum theory is that its predictions are probabilistic. If you are doing an experiment in a lab and using quantum theory to predict the outcome of various measurements, at best the theory can only predict the likelihood of the outcome: for example, 50% for predicting the outcome and 50% for it being different. The role of the quantum state is to determine the probability of outcomes. If the quantum state is known, you can calculate the probability of getting any possible outcome for any possible experiment.
Does the quantum state represent an objective aspect of reality, or is it just a way of characterizing us, that is, what a person knows about reality? This question was actively discussed at the very beginning of the study of quantum theory and has recently become topical again, inspiring new theoretical calculations and subsequent experimental verifications.
“If you change only your knowledge, things will no longer seem strange.”
To understand why a quantum state illustrates someone's knowledge, imagine a case in which you are calculating a probability. Before your friend rolls the dice, you guess which side they will land on. If your friend rolls a regular six-sided die, the probability that your guess will be correct will be approximately 17% (one sixth), no matter what you guess. In this case, the probability says something about you, namely, what you know about the die. Let's say you turn your back while throwing, and your friend sees the result - let it be six, but you do not know this result. And until you turn around, the outcome of the roll remains uncertain, even though your friend knows it. Probability representing human uncertainty, even if reality is certain, is called epistemic, from the Greek word for "knowledge".
This means that you and your friend could determine different probabilities, and neither of you would be wrong. You will say that the probability of rolling a six on the die is 17%, and your friend, who already knows the result, will call it 100%. This is because you and your friend know different things, and the probabilities you named represent different degrees of your knowledge. The only incorrect prediction would be one that rules out the possibility of a six coming up at all.
For the past fifteen years, physicists have wondered whether a quantum state could be epistemic in the same way. Suppose some state of matter, such as the distribution of particles in space or the outcome of a game of dice, is certain, but you don't know. The quantum state, according to this approach, is just a way of describing the incompleteness of your knowledge about the structure of the world. In different physical situations, there may be several ways to define a quantum state, depending on the known information.
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It is tempting to think of a quantum state in this way because it becomes different when the parameters of a physical system are measured. Making measurements changes this state from one where each possible outcome has a non-zero probability to one where only one outcome is possible. This is similar to what happens in a game of dice when you know the result. It may seem strange that the world can change just because you take measurements. But if it's just a change in your knowledge, it's no longer surprising.
Another reason to consider a quantum state to be epistemic is that it is impossible to determine what the quantum state was like before it was carried out using a single experiment. It also resembles a game of dice. Let's say your friend offers to play and claims that the probability of rolling a six is only 10%, while you insist on 17%. Can one single experiment show which one of you is right? No. The fact is that the resulting result is comparable to both probability estimates. There is no way to know which of the two of you is right in each case. According to the epistemic approach to quantum theory, the reason why most quantum states cannot be determined experimentally is like a game of dice: for every physical situation there are several probabilities consistent with the multiplicity of quantum states.
Rob Speckens, a physicist at the Institute for Theoretical Physics in Waterloo, Ontario, published a paper in 2007 in which he presented a "toy theory" designed to mimic quantum theory. This theory is not exactly analogous to quantum theory, as it is simplified to an extremely simple system. The system has only two options for each of its parameters: for example, "red" and "blue" for color, and "top" and "bottom" for position in space. But, as with quantum theory, it included states that could be used to calculate probabilities. And the predictions made with its help coincide with the predictions of quantum theory.
Speckens' "toy theory" was exciting because, as in quantum theory, its states were "undefinable" - and this uncertainty was entirely due to the fact that the epistemic theory does indeed relate to real physical situations. In other words, the "toy theory" was similar to the quantum one, and its states were uniquely epistemic. Since in the case of rejection of the epistemic view, the uncertainty of quantum states does not have a clear explanation, Speckens and his colleagues considered this sufficient reason to consider quantum states also epistemic, but in this case, the "toy theory" should be extended to more complex systems ( i.e. physical systems explained by quantum theory). Since then, it has led to a number of studies in which some physicists tried to explain all quantum phenomena with its help, while others tried to show its fallacy.
"These assumptions are consistent, but that doesn't mean they're true."
Thus, opponents of the theory raise their hands higher. For example, one widely discussed 2012 result published in Nature Physics showed that if one physics experiment can be performed independently of another, then there can be no uncertainty about the "correct" quantum state describing that experiment. That. all quantum states are "correct" and "correct", except for those that are completely "unreal", namely: "incorrect" are states like those when the probability of rolling a six is zero.
Another study published in Physical Review Letters in 2014 by Joanna Barrett and others showed that the Speckens model cannot be applied to a system in which each parameter has three or more degrees of freedom—for example, red, blue, and green for colors, and not just "red" and "blue" - without violating the predictions of quantum theory. Proponents of the epistemic approach propose experiments that could show the difference between the predictions of quantum theory and the predictions made by any epistemic approach. Thus, all the experiments carried out within the framework of the epistemic approach could be consistent to some extent with the standard quantum theory. In this regard, it is impossible to interpret all quantum states as epistemic, since there are more quantum states, and epistemic theories cover only a part of quantum theory, because they give results different from those of the quantum one.
Do these results rule out the idea that a quantum state indicates characteristics of our mind? Yes and no. Arguments against the epistemic approach are mathematical theorems that are proven by a particular structure applied to physical theories. Developed by Speckens as a way of explaining the epistemic approach, this framework contains several fundamental assumptions. One of them is that the world is always in an objective physical state, independent of our knowledge about it, which may or may not coincide with the quantum state. Another is that physical theories make predictions that can be represented using standard probability theory. These assumptions are consistent, but this does not mean that they are correct. The results show that in such a system there cannot be results that are epistemic in the same sense as Speckens' "toy theory" as long as it is consistent with quantum theory.
Whether you can put an end to this depends on your view of the system. Here opinions differ.
For example, Owee Maroni, a physicist and philosopher at the University of Oxford and one of the authors of a paper published in 2014 in Physical Review Letters, said in an email that "the most plausible psi-epistemic models" (i.e. those that can be fitted to the system Speckens) are excluded. Also, Matt Leifer, a physicist at the University of Champagne who has written many papers on the epistemic approach to quantum states, said that the issue was closed back in 2012 - if you, of course, agree to accept the independence of the initial states (which Leifer tends to).
Speckens is more vigilant. He agrees that these results severely limit the application of the epistemic approach to quantum states. But he emphasizes that these results are obtained within his system, and as the creator of the system, he points out its limitations, such as assumptions about probability. Thus, the epistemic approach to quantum states remains relevant, but if so, then we need to reconsider the basic assumptions of physical theories, which many physicists accept without question.
Nevertheless, it is clear that significant progress has been made in fundamental questions of quantum theory. Many physicists tend to call the question of the meaning of a quantum state merely interpretive, or worse, philosophical, as long as they don't have to develop a new particle accelerator or improve a laser. Calling the problem "philosophical", we seem to take it out of the redistribution of mathematics and experimental physics.
But work on the epistemic approach shows the illegitimacy of this. Speckens and his colleagues took the interpretation of quantum states and turned it into a precise hypothesis, which was then filled with mathematical and experimental results. This does not mean that the epistemic approach itself (without mathematics and experiments) is dead, it means that its advocates need to put forward new hypotheses. And this is an undeniable progress - for both scientists and philosophers.
James Owen Weatherall is Professor of Logic and Philosophy of Science at the University of Irvine, California. His latest book, Strange Physics of the Void, examines the history of the study of the structure of empty space in physics from the 17th century to the present day.