Accueil Sciences The bizarre world of quantum interpretations

The bizarre world of quantum interpretations

par Palantir Dewuka

To ordinary people, most quantum theories seem strange, while others seem downright bizarre. There are many theories that try to explain the intricacies of quantum systems and how our interactions affect them. And, not surprisingly, each approach is supported by its group of qualified and respected scientists.

Is it reasonable that you can modify a quantum system just by looking at it? What about creating multiple universes just making a decision? Or what if your mind divides because you have measured a quantum system?

You might be surprised to find that some or all of these things could happen regularly millions of times every day without you even realizing it.

The classical world (the world we live in) has a set of rules and the quantum world has a different set of rules. But of course, they describe the same unique universe. As far as physics is concerned, there are two realities: there is that which we experience every day, where a single object is a single object and nothing teleports through the walls or exists in two places at the times, and then there is that of the subatomic, that is to say the very, very small, where these rules no longer hold. These are respectively the worlds of classical physics (which follows Newton’s laws) and quantum (which follows laws which we do not understand). But everything is made up of quantum particles if you look closely and that means that a lot more of your daily experiences come down to quantum physics than you might think.

Olécio partenaire de Wukali

Light is a popular example of the strangeness of the quantum world. It exists simultaneously in the form of a continuous wave and a discrete particle known as the photon.

The most famous demonstration of this bizarre phenomenon is the double-slit experiment, where individual photons that pass through a wall with two slits produce patterns on a screen as if all of these waves were interacting until you set up a motion detector. photons to measure the slits crossed by each photon, at this time, they produce two light lines as if they were individual photons.

The idea is that quantum particles exist both as particles and as waves, also known as superposition, until they are measured or observed, when they collapse into a single state.

Your eyes create an image of the world with the light that hits your retina. Is it an exaggeration to call them photon detectors? According to recent research, no: studies suggest that humans may be able to detect a single photon at a better rate than chance. This opens up the intriguing possibility that our eyes can also detect quantum phenomena. “

Your sense of touch is also based on the quantum world. Even the densest object you’ve ever held is mostly made up of empty space. Indeed, matter is made up of atoms and atoms are made up of a very small nucleus surrounded by even more tiny electrons orbiting at a relatively huge distance. If you were to explode the nucleus to the size of a ball, you would have to travel the length of a football field to reach the most distant electrons.

Wolfgang Pauli and Niels Bohr spinning a Tippe Top at the Institute of Physics at University of Lünd, Sweden, July 1954

Things only seem solid because of quantum physics, that’s Pauli’s exclusion principle, to be precise. At its core, this principle says that there is a limit to the number of electrons that can drag in a specific orbit around an atom. For an electron from an atom in your hand to merge into an atom in your cup of coffee, it would take more energy than your hand is ready to exert. Instead, these electrons repel each other, making you feel like you’re touching a solid object.

Sight and touch are not necessarily the only senses that invoke quantum physics; the hair cells in your inner ear are sensitive to movement on the subatomic scale, for example. Until now, scientists have not explored the fundamental particles at work in the sense of hearing and taste. Who knows, we may discover that every phenomenon in classical physics that we know is really the work of quantum physics. Who said there was a dividing line between the two anyway?

For example, in the classical world in which we believe we live, we know that an object moving in a straight line at a speed of 100 km / h will travel 100 km in one hour. It works the same way every time. If an external force acts on the object, we can calculate a new displacement rate with relative ease. If we know the speed of the object and the position of the object, we can determine where it will be in the future.

Quantum mechanics does not care much about time. Because subatomic particles do not just act like ordinary objects, they also act like waves. We cannot make the same determinations on objects over time on the quantum scale as on the classical scale.

We cannot know at the same time the position and the speed of a quantum object because, in quantum mechanics, all the results can be also possible. It can get confusing when you’re dealing with endless possibilities, so let’s break them down into two possibilities: here and not here.

Right now, you are you and the things you see that seem to exist. The screen in front of you is real, as far as you can see. But your classical perspective limits your understanding of reality to those things that you can feel, the experience is cognitive. According to Copenhagen’s interpretation of quantum mechanics, this screen is only there because you have observed it. The myriad of positions that an object’s waveforms can ultimately take are like untrained predictions that wait for someone like you to come, take action (by simply observing) and cause the universe to move the reality of the object. Basically you are a god, you determine what is real by reason of your existence and your observations

Maybe you don’t want to believe that you are a god. Perhaps you are more comfortable with the idea that reality is real, whether people are there to observe it or not. It makes sense, doesn’t it? It is essentially the interpretation of the pilot wave theory of Louis de Broglie and David Bohm, whose beginnings date back almost a century (1927). This interpretation is deterministic, it says that everything was already going to be what it ends up being and there was never any ambiguity about it. It does not require an observer, so in this model our existence is useless.

This is no doubt the reason why another interpretation, the theory of multiple worlds (MWI), is gaining popularity. The theory of multiple worlds is the opposite of that of the pilot wave: it says that every possibility is real and manifests itself through infinite universes. You are alive in this universe, dead in another, Peter in the next and Michael in the fourth. Everything is not only possible, but defined in a reality with infinite universes.

This brings us to the interpretation that says “you are not a god, I am.” I am referring to the overall theory of quantum mechanics. This explains that everything is possible, but that only one result must appear. The universe itself prepares an infinite number of systemic possibilities, a series of events that will lead to eventual reality and hide it until the observer (that is, you) measures it. It’s like the universe is a restaurant with a menu that offers endless dishes always prepared, and would be happy to serve me whatever I want at some point.

However, I guess it could be your universe and I am just lucky enough to have been observed. In this case, thank you.

There are other interpretations, but these are among the most widespread and popular in the world of physics. It should be mentioned that, while these theories are definitely crazy, they also represent the most intelligent collective knowledge of our species, the most determined scientists have managed to come up with more than a century of study.

There is no simple, boring theory that links the quantum and classical world in as successful a way (and resists scientific rigor) as quantum mechanics and its many interpretations.

Quantum mechanics describes fundamental natural phenomena that are not accessible to direct human perception. As might be expected, empirical evidence shows that the phenomena of the quantum world are simply not compatible with classical images, notions, relationships created by perceptions of the classical world directly accessible to human senses. The undeniably natural empirical fact is that the quantum world cannot be expressed in terms of the language of the classical world. The only solution found by the great physicists (Schrödinger, Heisenberg, Pauli and others) is that quantum phenomena can be fully described by the formal language of mathematics.

Quantum physics is arguably the greatest intellectual triumph in the history of human civilization, but for most people, it seems to be too distant and abstract to matter. When we speak of quantum physics, we generally underline the strange and counterintuitive phenomena: Schrödinger’s cat in a superposition of “living” and “dead”, Einstein‘s objection with his famous phrase « God does not play dice with the universe », the strange long-distance correlations of quantum entanglement. These things are exciting because they are exotic, but studying them in the laboratory requires isolating very simple quantum systems, and it can be difficult to see a connection between these phenomena and everyday life.

Although quantum mechanics was invented to account for subatomic objects, such as photons and atoms, many experiments have established that quantum mechanics also applies to the macro world. The universe of quantum mechanics is fundamentally different from our classical perception of the world. Secular experiments have proven the validity of quantum theory. In fact, quantum mechanics is by far the most accurate and reliable science that humans have ever grasped.

In fact, quantum physics is all around us. The universe as we know it works on quantum rules, however the classical physics that emerges when you apply quantum physics to a huge number of particles looks very different, there are a lot of everyday familiar phenomena that owe their existence with quantum effects.

Strange effects occur on the atomic scale. Even if we don’t notice it in everyday life, quantum physics works all the time and everywhere. An atom, for example, is largely made up of more than 99% vacuum, there is nothing between the nucleus and the electronic layers that surround it. And if the atom had the dimensions of a stadium, the nucleus would be equivalent to a grain of sand. Logically, therefore, we should be able to get through walls, which is clearly not the case.

So why ? The answer lies in a curious phenomenon, the Pauli exclusion principle, which claims that two electrons cannot be in the same quantum state. As a result, two nearly identical electrons repel each other when they get too close. It is this principle which gives objects their solidity even though they are almost entirely constructed of vacuum.

A person who sits on a chair, for example, feels like touching it. In reality, this person floats about a nanometer from him, repelled by quantum and electrical forces. In other words, tiny atomic forces always keep us from actually touching something. If someone knew how to neutralize the principle of exclusion, we could therefore play the wall pass.

Quantum theory not only prevents atoms from falling on top of each other, it also allows them to bond together to form molecules. Let us imagine for the occasion an atom like a small solar system, made up of planets revolving around a star. If two of these systems intersect, they will destroy each other because the planets will bump into each other or escape in all directions. Logically, two atoms should therefore destroy themselves by meeting.

In other words, if quantum physics suddenly broke down, the molecules would break up knocking against each other and we would disappear in a gas of particles. This theory explains why atoms, rather than disintegrate, bond together to form matter.

Among the amazing properties of quantum theory, let us mention at least these :

– It is impossible to know exactly the position and the speed of a particle, there is always an uncertainty.
– From a certain point of view, a particle can be found at the same time in two different places.
– A particle exists as a combination of different simultaneous states, the axis of a rotating particle, for example, can point up and down.
– You can disappear and reappear elsewhere.

All of these properties seem implausible at first. In fact, according to Einstein himself: “The more the quantum theory works, the more crazy it seems“. Nobody knows where these strange laws spring from, which are only postulates, admitted without any other form of explanation. But quantum theory has at least one great advantage: its accuracy. Its validity was measured with an accuracy of 1 in 10 billion, an absolute record in the matter.

And if we do not perceive anything of this world in the course of our daily life, it is that we are made up of billions and billions of atoms (approximately 1028 is written with a number 1 followed by 28 zeros) and that the effects quantum, in a certain sense, compensate each other.

René Magritte. Variante de la Tristesse, 1957, oil on canvas, 50x60cm
Kerry Stokes Collection Perth ©Adagp Paris 2016

Throughout your life, it is certain that you feel things by touching it. Things that surround you in the physical world, such as your phone, computer, or the clothes you are wearing right now.

Everything you can feel and touch around you is made of atoms, atoms concentrated in a small component of matter. The specialization that studies this is quantum physics, it gives us many phenomena that are often incredible to understand about the world around us. In particular, the invisible movements continue at the atomic level.

You would think that the atomic world is not part of our daily life. We cannot see it and we cannot touch it. However, this information is a crucial point when it comes to our understanding of how the four fundamental forces shape the physical world, and therefore, the key to understanding the universe. After all, you can’t understand how big things work without knowing the ins and outs, small intricacies too.

Among the phenomena, we have quantum entanglement, particles that appear and disappear. Quantum mechanics also tells us that we are made up of particles. This means that at the microscopic level, all kinds of strange things are happening to us, which are not visible to the human eye, things that sometimes seem to make little sense, says quantum physics.

To understand the reason why you can never touch anything, you need to know how electrons work. To understand this, you need to know a minimum of information about the structure of atoms.

Almost the entire (palpable) mass at the atomic level is concentrated in incredibly small parts called the nucleus.

The surrounding area of ​​the nucleus is a space, with the exception of areas inside an atom where electrons and protons can be found orbiting the central nucleus of the nucleus. The number of electrons in an atom depends on the element that each atom is supposed to contain.

Like photons, a subatomic part also has the particle-wave duality, which means that the electron has the characteristics of both a particle and a wave. On the other hand, they also have a negative charge. Particles are, by their nature, attracted by particles of opposite charge and they reject other particles of similar charge, such as magnetic poles, according to quantum physics.

This practice prevents electrons from coming into direct contact. Their wave packets, on the other hand, can overlap, but never touch.

The same goes for all of humanity. When you sit on a chair or slip into your bed, the electrons in your body repel the electrons that make up the chair. You hover over it at an unfathomable distance.

So if the repulsion of electrons prevents us from really touching anything, why do we perceive touching it as a real thing? The answer comes down to how our brains interpret the physical world.

Many factors come into play in this area. The nerve cells that make up our body send signals to our brain that tell us that we are physically touching something. When touch is simply given to us by the interaction of our electrons, the electromagnetic field permeates space-time (average electronic waves propagate through).

It should be noted that various things play a role here to transform collections of particles into tangible objects. We have things like chemical bonding and, of course, the four main forces mentioned above. Chemical bonds allow electrons to “cling” to imperfections on the surface of an object, creating friction.

You will see that the purely electrostatic repulsion between the electrons is not the only reason why you fly over your chair. In the typical case, it is about as strong as Pauli’s exclusionary principle when it comes to separating things. It is a combination of these two effects dominating real behavior. This principle explains an incredible idea that the electrons know where all the other electrons are. They try to avoid each other as much as possible, which results in an exponential decrease in the force between the electrons. They do so even without the electromagnetic repulsion at play.

All in all, isn’t it amazing how these things are related? It is a basic scientific truth that things are often not as they seem, or at least they are not as we perceive them.

electrons, the electromagnetic field permeates space-time (average electronic waves propagate through).

It should be noted that various things play a role here to transform collections of particles into tangible objects. We have things like chemical bonding and, of course, the four main forces mentioned above. Chemical bonds allow electrons to “cling” to imperfections on the surface of an object, creating friction.

Here’s what says writer and playwright Tom Stoppard

The world of particles is the intelligence officer’s dream. An electron can be here or there at the same time. He can go from here to there without going through the intermediate positions; it can pass through two doors simultaneously, or from one to the other by a path visible to all, until someone looks, in which case it will take another path. His movements are unpredictable because they are without reason. [The electron] thwarts all surveillance because when you know what it is doing you cannot know where it is, and when you know where it is you ignore what it is doing: it is because of the principle of Heisenberg’s uncertainty. It is not because you do not look with enough care, it is because there is nothing like an electron having a defined position and a defined [speed]; if you have one, you lose the other; and all of this is done without rigging, it’s the real world. “

In the impossibility of concluding such a subject, let us leave the last word to Max Planck, it is wiser … « Science cannot solve the ultimate mystery of nature. And that is because, in the final analysis, we are ourselves a part of the mystery that we are trying to solve. »

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