The observer alters what he sees! Some events happen only because they are observed, if there was nobody to see them they would not exist. This is the very meaning of the experience known as "Schrödinger cat". In **1935** the physicist Erwin Schrodinger devised an experiment with a cat in the real world, boxed and sealed opaque. In this box a device kills the animal when it detects the decay of a radioactive atom of the quantum world. In the quantum world a radioactive atom such as a uranium atom can exist in two superposed states: intact and disintegrated. This superposition state ceases immediately when there is observation, then we say that there is decoherence when a system A and B becomes an A or B. If the probabilities indicate that disintegration has an even chance of having occurred after one minute, quantum mechanics states that, as compliance is not made, the atom is simultaneously in two states: intact and disintegrated. But the diabolical mechanism, devised by Erwin Schrödinger cat state binds to the status of radioactive particles, so the cat would be simultaneously in two states (the state of live and dead) to the opening the box. | | As the observation triggers the choice between the two states, we simply can not tell if the cat is dead or not after a minute. Our brain is not ready to accept this kind of situation for a macroscopic object in the real world as a particle, our mind accepts design the wave function What follows. Historically, the wave function was introduced by Louis de Broglie in his thesis in 1924. Its name reflects the fact that it gives every particle, the interference properties of a wave, generalized wave-particle duality of light introduced by Max Planck. This situation is not feasible a pure thought experiment because you can never be measured, that the cat is both dead and alive, is to try to determine its state necessarily causes the collapse of the wave function, inseparable two distinct states. These statements are conceivable bunk when systems are defined by wave functions. But as regards the Schrödinger cat, our mind refuses to admit that until the box is not open, and we did not find the condition of the cat, the cat is neither dead nor alive. The mystery of the Universe may be described in the depths of the atom. | | ### Image: Illustration © Mylène Simoès, Art Director. Where does the choice of cat for this thought experiment? Maybe this is a reference from Schrödinger cat Cheshire. |

The **Cheshire Cat** is a fictional character that we see in Alice in Wonderland by Lewis Carroll. Malin and philosopher, it escapes to order beheading of the Queen of heart by making its transparent body. The cat appears and disappears so sublime, creating fun at Alice. The cat sometimes puts its foot on philosophical issues that interfere with Alice. At one point in history, the cat disappears completely until it is left of him was his smile. This tale is a delight when the absurdity follows a rigorous logic. The characters are unforgettable as the White Rabbit, March Hare, the Hatter, the Queen of Heart, but especially the Cheshire Cat. This cat is one of the few characters that Alice meets, which seems reasonable. Yet it describes himself as crazy as opposed to the dog growls when it is happy and wags its tail when it is angry. | | This is also the paradox of Alice in Wonderland, proved to be fools think normal and the few that are supposed to believe themselves crazy. ### Image: The Cheshire Cat and his strange feature, click on the image of the cat to watch the video on facebook. The Cheshire Cat, in Alice au Pays des Merveilles (**1865**) | | |

Quantum theory describes the microscopic world of objects differently than macroscopic objects, i.e. our scale in the classical world. For example, in the classical world, the position and speed of a car, are well defined. In the quantum world, it is impossible to know simultaneously and precisely the position of a particle and its speed. Experts call the Heisenberg inequality set in 1927 by German physicist Karl Werner Heisenberg. In quantum mechanics, it is not possible to know exactly the value of a parameter without measuring it. The mathematical theory describes a state not by a torque, speed and position precisely, but by a wave function that calculates the probability of finding the particle at one point. Hence the probabilistic nature of quantum mechanics who predicted that particles are waves and not only material points. Therefore it can be in two places at once. Imagine the state of a particle is fully described by its color, which may take only two values, red or blue. In our world, the two colors, so both states are perfectly distinguishable. In the world of quantum states that are both red and blue exist.
| | Only observation reveals the property red or blue system. Without it, the object has two properties. That is why a quantum system must be described generally without separating an object from another, although they may be spatially separated. This is called entangled state. Entanglement (Latin intricare, confuse) means in ordinary language "entanglement", Quantum entanglement means that any set of quantum objects can be put in a superposition of states. Each of these statements describes several objects at once, whose properties are linked. If the object 1 is in a certain state, it partly determines the state of the object 2. Even if they are separated by large spatial distances, the two systems are not independent and must be considered {S1 + S2} as a single system. Quantum mechanics explains the existence of matter, is for scientists, the greatest intellectual adventure of the 20th century. | | ### Image: Researchers have managed to entangle the vibrations of two pairs of ions. This strange relationship that is quantum entanglement, is shown in this image. Ions are as interconnected by a spring and each pair oscillates (John Jost and Jason Amini). |