What is the Copenhagen interpretation?

Copenhagen interpretation is the explanation.quantum mechanics, formulated by Niels Bohr and Werner Heisenberg in 1927, when scientists worked together in Copenhagen. Bohr and Heisenberg were able to improve the probabilistic interpretation of the function formulated by M. Born, and tried to answer a number of questions, the emergence of which is due to wave-wave dualism. This article will discuss the main ideas of the Copenhagen interpretation of quantum mechanics, and their influence on modern physics.

Problems

Interpretations of quantum mechanics calledphilosophical views on the nature of quantum mechanics, as a theory that describes the material world. With their help, it was possible to answer questions about the essence of physical reality, the method of its study, the nature of causality and determinism, as well as the essence of statistics and its place in quantum mechanics. Quantum mechanics is considered to be the most resonant theory in the history of science, but a consensus in its deepest understanding still does not exist. There are a number of interpretations of quantum mechanics, and today we will get acquainted with the most popular of them.

Main ideas

As you know, the physical world consists of quantumobjects and classical measuring instruments. The change in the state of measuring instruments describes the irreversible statistical process of changing the characteristics of micro-objects. When a micro-object interacts with the atoms of a measuring device, the superposition is reduced to one state, that is, the wave function of the measuring object is reduced. The Schrödinger equation does not describe this result.

In terms of the Copenhagen interpretation,Quantum mechanics does not describe micro-objects by themselves, but their properties, which manifest themselves in the macro-conditions created by typical measuring instruments under observation. The behavior of atomic objects cannot be distinguished from their interaction with instruments for measurements that fix the conditions for the origin of phenomena.

A look at quantum mechanics

Quantum mechanics is a static theory.This is due to the fact that measuring a micro-object leads to a change in its state. So there is a probabilistic description of the initial position of the object, described by the wave function. The complex wave function is the central concept of quantum mechanics. The wave function changes to a new measurement. The result of this measurement depends on the wave function, in a probabilistic way. The physical value has only the square of the modulus of the wave function, which confirms the probability that the microobject under study is located in a certain place in space.

In quantum mechanics, the law of causalityperformed with respect to the wave function, which varies in time depending on the initial conditions, and not relative to the coordinates of the velocity of particles, as in the classical interpretation of mechanics. Due to the fact that only the square of the modulus of the wave function is endowed with a physical value, its initial values ​​cannot be determined in principle, which makes it impossible to obtain exact knowledge about the initial state of the quanta system.

Philosophical basis

From a philosophical point of view, gnoseological principles are the basis of the Copenhagen interpretation:

1. Observability. Its essence lies in the exclusion from the physical theory of those statements that can not be verified by direct observation.
2. Add-ons. It assumes that the wave and particle description of the objects of the microworld complement each other.
3. Uncertainties. He says that the coordinate of micro-objects and their impulse cannot be determined separately, and with absolute accuracy.
4. Static determinism.It assumes that the present state of the physical system is determined by its previous states not unequivocally, but only with a share of the likelihood of the tendencies of change inherent in the past.
5. Matches According to this principle, the laws of quantum mechanics are transformed into the laws of classical mechanics, when it is possible to neglect the magnitude of the quantum of action.

Benefits

In quantum physics, information about atomic objects,obtained through experimental installations, are in a peculiar relationship with each other. In the Werner-Heisenberg uncertainty relations, an inverse proportionality is observed between the inaccuracies in the fixation of kinetic and dynamic variables that determine the state of a physical system in classical mechanics.

The weighty advantage of CopenhagenThe interpretation of quantum mechanics is the fact that it does not operate with detailed statements directly about physically unobservable quantities. In addition, with a minimum of prerequisites, it builds a conceptual system that exhaustively describes the experimental facts that are currently available.

The meaning of the wave function

According to the Copenhagen interpretation, the wave function can be subject to two processes:

1. Unitary evolution, which is described by the Schrödinger equation.
2. Measurement.

Tangent first process in academiano one had any doubts, and the second process sparked discussions and generated a number of interpretations, even within the framework of the Copenhagen interpretation of consciousness itself. On the one hand, there is every reason to believe that the wave function is nothing but a real physical object, and that it undergoes a collapse during the second process. On the other hand, the wave function may not be a real entity, but an auxiliary mathematical tool, the only purpose of which is to provide an opportunity to calculate the probability. Bohr emphasized that the only thing that can be predicted is the result of physical experiments, so all minor issues should relate not to exact science, but to philosophy. He professed in his workings the philosophical concept of positivism, requiring that science discuss only realistically measured things.

Double-slit experience

In a double-slit experience, the light passing through twoslits, falls on the screen, on which two interference fringes appear: dark and light. This process is explained by the fact that light waves can in one place mutually amplify, while in others they can be mutually quenched. On the other hand, the experiment illustrates that light has the properties of a stream of a part, and electrons can exhibit wave properties, while giving an interference pattern.

It can be assumed that the experiment is carried out with the flowphotons (or electrons) are so low in intensity that only one particle passes through the slits each time. However, when adding photon hit points onto the screen, the same interference pattern is obtained from the overlapping waves, despite the fact that the experience concerns allegedly separate particles. This is explained by the fact that we live in a “probabilistic” universe, in which every future event has a redistributed degree of possibility, and the likelihood that something completely unforeseen happens at the next moment in time is rather small.

Your questions

The gap experience raises the following questions:

1. What will be the rules of behavior of individual particles?The laws of quantum mechanics point to the place of the screen in which the particles will appear, statistically. They allow you to calculate the location of the light bands, in which, most likely, there will be a lot of particles, and dark bands, where less particles are likely to fall. However, the laws that govern quantum mechanics cannot predict where a particular particle will actually be.
2. What happens to a particle betweenemission and registration? According to the results of observations, it may give the impression that the particle is in interaction with both slits. It seems that this is contrary to the laws of the behavior of a point particle. Moreover, when a particle is registered, it becomes a point.
3. Under the action of which the particle changes its behaviorfrom static to nonstatic, and vice versa? When a particle passes through the slits, its behavior is caused by a non-localized wave function that simultaneously passes through both slits. At the time of registration of a particle, it is always fixed as a point wave, and a blurred wave packet is never obtained.

Answers

The Copenhagen theory of quantum interpretation answers the questions posed as follows:

1. Fundamentally impossible to eliminate probabilisticthe nature of the predictions of quantum mechanics. That is, it cannot accurately indicate the limitation of human knowledge of any hidden variables. Classical physics refers to probability in those cases when it is necessary to describe a process like throwing dice. That is, probability replaces incomplete knowledge. On the contrary, the Copenhagen interpretation of quantum mechanics by Heisenberg and Bohr states that the measurement result in quantum mechanics is fundamentally non-deterministic.
2. Physics is a science that studies results.measuring processes. To think about what is happening in their consequence is illegal. According to the Copenhagen interpretation, questions about where the particle was before its registration, and other similar fabrications are meaningless, and therefore should be excluded from the reflections.
3. Act of measurement leads to instant collapsewave function. Consequently, the measurement process randomly selects only one of the possibilities that the wave function of a given state allows. And to reflect this choice, the wave function must change instantly.

Formulations

Wording of copenhagen interpretation inThe original form spawned several variations. The most common of them is based on the approach of consistent events and such a concept as quantum decoherence. Decoherence makes it possible to calculate the fuzzy boundary between the macro and micro worlds. The remaining variations differ in the degree of "realism of the wave world."

Criticism

The usefulness of quantum mechanics (answerHeisenberg and Bohr to the first question) was questioned in a mental experiment conducted by Einstein, Podolsky and Rosen (EPR paradox). Thus, scientists wanted to prove that the existence of hidden parameters is necessary so that the theory does not lead to instantaneous and non-local "long-range action". However, during the EPR paradox check, which became possible due to Bell's inequalities, it was proved that quantum mechanics is correct, and various theories of hidden parameters do not have experimental confirmation.

But the most problematic was the answer of Heisenberg and Bohr to the third question, which put the measurement processes in a special position, but did not determine the presence of distinctive features in them.

Многие ученые, как физики, так и философы, flatly refused to accept the Copenhagen interpretation of quantum physics. The first reason was that the interpretation of Heisenberg and Bohr was not deterministic. And the second is that it introduced an indefinite concept of measurement that turned probabilistic functions into reliable results.

Einstein was confident that the description of the physicalreality, given by quantum mechanics in the interpretation of Heisenberg and Bohr, is incomplete. According to Einstein, he found logic in the Copenhagen interpretation, but his scientific instincts refused to accept it. Therefore, Einstein could not abandon the search for a more complete concept.

In his letter to Born, Einstein said:"I am sure that God does not roll the dice!" Nils Bohr, commenting on this phrase, told Einstein not to tell God what to do. And in his conversation with Abraham Pais, Einstein exclaimed: “Do you really think that the Moon exists only when you look at it?”.

Erwin Schrödinger invented a thought experiment withBy means of which he wanted to demonstrate the inadequacy of quantum mechanics during the transition from subatomic to microscopic systems. At the same time, the necessary collapse of the wave function in space was considered problematic. According to Einstein's theory of relativity, instantaneousness and simultaneity make sense only for an observer who is in the same frame of reference. Thus, there is no time that could become one for all, which means that instantaneous collapse cannot be determined.

Spread

Неофициальный опрос, проведенный в научных кругах in 1997, showed that the previously dominant Copenhagen interpretation, briefly discussed above, is supported by less than half of the respondents. Nevertheless, she has more adherents than other interpretations separately.

Alternative

Many physicists have a closer interpretation.quantum mechanics, which was called "no." The essence of this interpretation is fully expressed in David Mermin's dictum: “Shut up and calculate!”, Which is often attributed to Richard Feynman or Paul Dirac.