6 facts about quantum physics that everyone should know

Unprepared student quantum physics scares from the experience. She's weird and counterintuitive, even to physicists who have dealing with it every day. But it is not incomprehensible. If you are interested in quantum physics, in fact there are six key concepts from it that you need to keep in mind. No, they have little to do with quantum phenomena. And it's not thought experiments. Just wrap them in us, and quantum physics will be much easier to understand.

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Everything is made of waves and particles, tooThere are many places from which to begin this discussion, and this is as good as any other: everything in our Universe has both particle nature and wave. If I had to say about magic: "Everything is waves and only waves", it would be wonderful poetic description of quantum physics. In fact, everything in this universe has a wave nature.

Of course, also everything in the Universe is of the nature of the particles. Sounds strange, but it is an experimental fact.

To describe real objects as particles and waves simultaneously will be somewhat inaccurate. Strictly speaking, the objects described by quantum physics are not particles and waves, but rather belong to the third category, which inherits the properties of waves (frequency, wavelength, together with the distribution in space) and some properties of particles (they can be counted and localized to a certain degree). This leads to a lively debate in the physical community on the topic of whether it proper to speak of light as a particle; not because there is a contradiction in whether the light nature of the particles, but because to call photons "particles" and not "quantum field excitations" is to introduce students astray. However, this also applies to whether to call electrons particles, but such disputes will remain in the purely academic circles.

This "third" nature of quantum objects is reflected in the sometimes confusing language of physicists discussing quantum phenomena. The Higgs boson was discovered at the Large hadron Collider as a particle, but you've probably heard the phrase "Higgs field", such delocalized things that fills all space. This occurs because, under certain conditions, like the experiments with the collision of particles is more appropriate to discuss the excitation of the Higgs field, rather than to determine characteristics of the particles, while under other conditions like a General discussion of why certain particles have mass, it is more appropriate to discuss the physics in terms of the interaction with the quantum field of universal proportions. It's just different languages describing the same mathematical objects.

Quantum physics discreteAll in the name of physics the word "quantum" comes from the Latin "how much" and reflects the fact that quantum models always include something coming in discrete quantities. The energy contained in the quantum field, comes in multiple quantities of a certain fundamental energy. For light is associated with the frequency and wavelength of light is high frequency light with a short wave characteristic has a great energy, while low frequency light with a long wavelength has a small characteristic energy.

In both cases, meanwhile, the total energy enclosed in a separate light field, integer multiples of this energy — 1, 2, 14, 137 times — and not to meet strange fractions like a half, "PI" or the square root of two. This property is also observed in discrete energy levels in atoms and energy bands specific — some of the energy values are permitted, others are not. Atomic clocks work because of the discreteness of quantum physics using a frequency of light associated with a transition between two allowed States in cesium, which allows you to save time at the level necessary for the implementation of the "second leap".

High-precision spectroscopy can also be used to find things like dark matter and remains part of the motivation for the work of the Institute the low-energy fundamental physics.

It's not always obvious — even some of the things quantum, in principle, like black-body radiation associated with a continuous distributions. But upon closer inspection and when you connect a deep mathematical apparatus of quantum theory becomes even more weird.

Quantum physics is probabilisticOne of the most amazing and (historically, at least) controversial aspects of quantum physics is that it is impossible with certainty to predict the outcome of an experiment with a quantum system. When physicists predict the outcome of a particular experiment, their prediction is of the form of the probability of finding each of the specific possible outcomes, and comparison between theory and experiment, always include the removal of the probability distribution of many repeated experiments.

The mathematical description of a quantum system usually takes the form of a "wave function" presented in equations, Greek beech psi: Ψ. There is much discussion about what exactly constitutes a wave function, and they divided physicists into two camps: those who see in the wave function a real physical thing (eticheskie theorists), and those who believe that the wave function is solely the expression of our knowledge (or lack thereof) regardless of the underlying state of the individual quantum object (epistemic theorists).

Each class of fundamental models of the probability of finding the result is not determined by the wave function directly, and the square of the wave function (roughly speaking, everything to her; the wave function is a complex mathematical object (and, hence, involves imaginary numbers like the square root or its negative), and the operation of obtaining the likelihood is a bit more complicated, but the "square wave function" is enough to understand the gist of the idea). This is known as the born rule in honor of the German physicist max born, who calculated it for the first time (in a footnote to the work in 1926) and surprised many people ugly his incarnation. Active work is ongoing in attempts to deduce the born rule from more fundamental principles; but so far none of them was successful, although it gave rise to a lot of interesting science.

This aspect of the theory also leads to the particles residing in multiple States simultaneously. All we can predict is the probability, before the measurement that produces a concrete result of the measured system is in the intermediate state — the state of superposition that includes all possible probabilities. But really if the system is in multiple States or in one unknown — it depends, do you prefer onicescu or epistemic model. They both lead us to the next point.

Quantum physics is nonlocalThe last great contribution of Einstein to physics was not widely recognized as such, mainly because he was wrong. In the work of 1935, together with his young colleagues Boris Padalkin and Nathan Rosen (EPR work), Einstein gave a clear mathematical statement of something that was bothering him for some time, what we call "confusion".

The work of EPR argued that quantum physics has acknowledged the existence of systems in which measurements taken at widely remote locations, can be correlated to the outcome of one determined another. They argued that this means that the measurements must be determined in advance, any common factor, because otherwise would be required to transfer the result from one measurement to the place of the other at a speed exceeding the speed of light. Therefore quantum physics must be incomplete, to be an approximation of a deeper theory (the theory of "local hidden variable" in which the individual measurements are not dependent on something that is further away from the measurements than can cover the signal travelling at the speed of light (locally), but rather is determined by some factor that is common to both systems in a confusing pair (a hidden variable).

It had been a strange footnote more than 30 years, as it seemed there was no way to verify it, but in the mid 60-ies of the Irish physicist John bell more elaborate the consequences of the EPR. Bell showed that you can find circumstances in which quantum mechanics predicts correlations between distant measurements, which will be stronger than any possible theory proposed like e, P and R. this is Experimentally checked in the 70-ies of the John Closer and Alain Aspect in the early 80's- they showed that these entangled systems can be potentially explained by any theory of local hidden variable.

The most common approach to understanding this result lies in the assumption that quantum mechanics is nonlocal: that the results of measurements made in a particular place may depend on the properties of a remote object so that it can not be explained using the signals, moving at the speed of light. This, however, does not allow to transmit information with superluminal speed, though there have been many attempts to circumvent this limit by using quantum nonlocality.

Quantum physics (almost always) associated with a very smallQuantum physics has a reputation of strange, because her predictions are radically different from our everyday experience. This is because its effects are the smaller, the larger the object you can hardly see the wave behavior of particles and the wavelength with increase in torque. The wavelength of a macroscopic object like a running dog are so ridiculously small that if you increase every atom in the room to the size of the Solar system, the wavelength of a dog's the size of a single atom in this solar system.

This means that quantum phenomena are mostly limited to the scale of atoms and fundamental particles, mass, and acceleration which are small enough that wavelength remained so small that it could not be observed directly. However, applied a lot of efforts to increase the size of the system showing quantum effects.

Quantum physics is not magicThe previous paragraph quite naturally leads us to this: no matter how strange quantum physics may seem, this is clearly not magic. What she posits, strange by the standards of everyday physics, but it is strictly limited to well-understood mathematical rules and principles.

So if someone comes to you with the "quantum" idea, which seems impossible — infinite energy, magic healing power, impossible space engine is almost certainly impossible. This does not mean that we cannot use quantum physics to do incredible things: we're constantly writing about the incredible breakthroughs using quantum phenomena, and they are already rather surprised mankind, it just means that we don't go beyond the boundaries of the laws of thermodynamics and common sense.

If the above points you seem a little, think of it as only a useful starting point for further discussion. published 


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Source: hi-news.ru


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