## How to understand the behavior of an electron?

Oct

7

2014

I want to tell you about one of the most beautiful ideas. It is a physical experiment, and it is beautiful because one elegant movement it expands our consciousness, making us understand that objects can behave in a way that we imagine and difficult. But interestingly, it can be calculated. It is beautiful because questioned the logic of the fundamental principles on which we have built our understanding of the world. Fine because deceptively simple to understand, but its effects scare. Hopefully, your picture of the world will be destroyed. Next – the text from the first-person narrator with Wired.

It was eleven years ago. I was a college freshman, sat in the physical laboratory, turning off the lights, and looked at a blank computer screen. Against the background of playing hits of the 80’s.

So, what I was given. On the table in front of me was a box with two thin slotted at one end. We shoot particles into the box through the cracks. I conducted an experiment with photons, particles of light, but it can be done and with the electrons, and, in principle, anything. It could even be the ball 60 carbon atoms, which is enormous compared to electrons. For convenience, I will refer to the objects of the experiment with electrons, but keep in mind that it can be any material that is broken into pieces.

At the other end of the box – a CCD camera that takes a picture when something gets into it. Every time a particle passes through the box, I can see how the corresponding point on the screen lights up my computer.

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For greater caution, we have set up the experiment so that at any given time inside the box can be only one particle. Imagine that a very tiny ball is thrown into the box. Music plays, we sit and wait.

What would you expect to see at the other end of the box? If the electrons behave like waves, you will see bright and dark bands, like ripples in a tank of water. This occurs because the waves interfere with each other, are extinguished, when the peak of one wave meets another, and are exacerbated when the peaks line up.

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But the electrons – do not worry it whole pieces. I know this because I can see how they come on the screen one at a time and beat in one place, like a drop of rain on asphalt. And if the electrons – a whole pieces, you will only see them piling up for the gap, and nowhere else. In short, you expect that they will behave like balls.

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And the truth is, if you are conducting an experiment with only one open slot, they behave like a ball, getting into the lane behind a strict open slot. Reasonable to assume that when we open both slits, we can see two bands – corresponding to each slot.

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What are the electrons?

See for yourself. In this video, made ​​by scientists Hitachi in 1989, you can see what they are doing electrons. Video speeded up to 30 times.

It takes time to understand how it’s weird. Either way, the electrons created this interference pattern of light and dark bands. But they went one by one, as they could interfere with each other? If you think of an electron as a tiny ball, you have to conclude that an electron passing through one slit, and slips through the other. He chooses both ways and interferes with itself. Complete nonsense.

Let’s go back and try to collect all the data. Comes the obvious question to be asked. Think of an electron, which came on the screen. Through which slit it passed?

Through the left?

No. Because when you cover the right slot, striped picture disappears and you’re left with a boring one strip.

Through the right?

No. For the same reason as above. If you close the left slit, you will again get boring stripes.

After both?

No. Because if that were true, we would expect to see, as the electron is divided into two parts, and one electron (or half of it) goes through every crevice. But if you put detectors on the slots, you will find that this is not happening. You will always see only one electron at a time. He never falls into two parts.

Anywhere else fails?

No. Of course not, what nonsense. If you will cover both slits, nothing will happen.

At this point, you begin to think that all of this is getting a little ridiculous. Why can not we just follow the damned electron and know which slit it passes? The problem is that looking at anything is to highlight it, and if you highlight an electron, it means to push him to the photon. If you are a tiny electron, such a blow will knock you out of the way.

But wait a minute here. Maybe if you do hit very, very soft, you will not disturb the electron? Bad luck is that if you make the light more tender (lower momentum), you make it more diffuse (increase the wavelength) and eventually not be able to tell which slit the electron has gone.

This is a dead end. Any scheme that you can come up with to determine the path of the electron, will destroy the interference pattern.

Summing up, we came to the striped pattern that is created by a single particle. But if you are trying to find out exactly how the particle is on the wall, you come to the conclusion that it does not choose the left route, do not choose the right route, do not choose both ways and does not give up either. As noted by MIT professor Allan Adams, it’s pretty much exhausted all logical possibilities.

Electronic not like a wave because, unlike the wave is incident on the screen at one point. Electron does not look like a ball, because if you throw it through a double slit, it interferes and forms a pattern of stripes. There is no analogy to help you understand what an electron. It’s fucking magic.

As they say in his lectures on kvantmehu Allan Adams:

These electrons are doing something, which we never thought of before, as never dreamed about even suitable words in the language is not.

It turns out that the empirical electrons have a way to travel and the existence of which is different from what we are used to. As the molecule. And bacteria. These objects are simply hard to find. Physicists have come up with the name of a model of existence. We call this superposition.

Sometimes it is useful to think of an electron as a particle, it is sometimes useful to think of it as a wave. But it’s just convenient for our speech, and how to name both incomplete. Electron – not a wave and a particle. Electron – is an electron. The same applies to the photon, the atom, a ball or a giant molecule, what have you been. The larger the object, the harder it is to see these bands.

Werner Heisenberg, one of the founders of quantum mechanics, it is well understood. In 1930, he wrote:

The solution is that the two mental pictures which forms we experiment – one with and one particle with wave – both incomplete and have only approximate analogies that are accurate only in certain cases. The apparent duality arises only because of the limitations of our language.

As taught by Heisenberg and others, although the language lets us down, we can come up with rules that explain exactly how tiny little things behave. These rules and there is quantum mechanics. Using these rules, complex physics can throw phrases like “the wave function of the electron is in a superposition and passes through the left and right of the gap.” These proposals are very accurately explained mathematical expressions, and based on them to make the most accurate experiments. What is missing is a coherent picture, which you can add up in my head and that will explain what path selects the electron. Moreover, we are pretty sure that this picture never goes.

There is nothing surprising in the fact that our monkey brains that evolved, throwing spears and rocks of medium size, can not visualize the behavior of very small things. But what is even more surprising that even though we can not imagine that the quantum world, we were able to work out the rules of the game.

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