Schrödinger's cat paradox

Schrödinger's cat paradox

Schrödinger's cat is the most popular paradox of quantum physics. It has different variants; Here we expose the simplest.

It was proposed by the Austrian Nobel Prize Erwin Schrödinger in 1935. It is a mental experiment that shows the disconcerting of the quantum world.

Imagine a cat inside a completely opaque box. Inside there is a mechanism that connects an electron detector to a hammer. And, just below the hammer, a glass jar with a dose of lethal poison to the cat. If the detector picks up an electron it will activate the mechanism, causing the hammer to fall and break the bottle.

An electron is fired. Logically, two things can happen. The detector may pick up the electron and activate the mechanism. In that case, the hammer falls, breaks the jar and the poison expands inside the box. The cat inhales and dies. When we open the box, we will find the dead cat. Or the electron may take another path and the detector will not pick it up, so the mechanism will never activate, the bottle will not break, and the cat will still be alive. In this case, when the box is opened, the cat will appear safe and sound.

So far everything is logical. At the end of the experiment we will see the cat alive or dead. And there is a 50% chance of one thing or the other happening. But quantum defies our common sense.

The electron is at the same time wave and particle. To understand it, it is shot like a bullet, but also, and at the same time, like a wave or like the waves that form in a puddle when we throw a stone. That is, take different paths at once. And they are not excluded, but overlap, as the water waves in the puddle would overlap. So it takes the path of the detector and, at the same time, the opposite.

The electron will be detected and the cat will die. And, at the same time, it will not be detected and the cat will remain alive. At the atomic scale, both probabilities are met simultaneously. In the quantum world, the cat ends up alive and dead at the same time, and both states are equally real. But, when we open the box, we only see it alive or dead.

What has happened? If both possibilities are fulfilled and real, why do we only see one? The explanation is that the experiment applies quantum laws, but the cat is not a quantum system. Quantum acts at a subatomic scale and only under certain conditions. It is only valid in isolated particles. Any interaction with the environment causes quantum laws to cease to apply.

Many particles together interact with each other, so quantum is not worth it in the big world, like the cat. Nor when there is heat, because heat is the movement of atoms interacting. And the cat is hot stuff. But the most surprising thing is that even we, when opening the box and observing the result of the experiment, interact and contaminate it.

So is. A curious characteristic of quantum is that the mere fact of observing contaminates the experiment and defines a reality in front of others. Einstein thus expressed his bewilderment: "Does this mean that the Moon is not there when nobody looks at it?"

Conclusion: when the quantum system is broken, reality is defined by one of the options. We will only see the cat alive or dead, never both. This process of transition from quantum reality to our classical reality is called decoherence, and is responsible for seeing the world as we know it. That is, a single reality.

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