The prevailing theory, called the Copenhagen interpretation, says that a quantum system remains in superposition until it interacts with, or is observed by, the external world. The EPR article highlighted the counterintuitive nature of quantum superpositions, in which a quantum system such as an atom or photon can exist as a combination of multiple states corresponding to different possible outcomes. Schrödinger intended his thought experiment as a discussion of the EPR article-named after its authors Einstein, Podolsky, and Rosen-in 1935. It is unclear which interpretation is correct the underlying issue raised by Schrödinger's cat remains an unsolved problem in physics. Interpretations for resolving this question include that the cat is dead or alive when the box is opened (Copenhagen) that a conscious mind must observe the box ( Von Neumann–Wigner) that upon observation, the universe branches into one universe where the cat is alive and another one where it is dead ( many-worlds) that every object (such as the cat, and the box itself) is an observer, but superposition is relative depending on the observer ( relational) that superposition never truly exists due to time-travelling waves ( transactional) that merely observing the box either slows or accelerates the cat's death ( quantum Zeno effect) among other theories that assert that the cat is dead or alive long before the box is opened. Experiments at the atomic scale have been carried out, showing that very small objects may be superimposed superimposing an object as large as a cat would pose considerable technical difficulties.įundamentally, the Schrödinger's cat experiment asks how long superpositions last and when (or whether) they collapse. As a result, Schrödinger's cat has had enduring appeal in popular culture. The experiment is not intended to be actually performed on a cat, but rather as an easily understandable illustration of the behavior of atoms.

The scenario is often featured in theoretical discussions of the interpretations of quantum mechanics, particularly in situations involving the measurement problem. Though originally a critique on the Copenhagen interpretation, Schrödinger's seemingly paradoxical thought experiment became part of the foundation of quantum mechanics. This poses the question of when exactly quantum superposition ends and reality resolves into one possibility or the other. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. The Copenhagen interpretation implies that, after a while, the cat is simultaneously alive and dead. a single atom decaying), the flask is shattered, releasing the poison, which kills the cat. a Geiger counter) detects radioactivity (i.e. In Schrödinger's original formulation, a cat, a flask of poison, and a radioactive source are placed in a sealed box. This thought experiment was devised by physicist Erwin Schrödinger in 1935 in a discussion with Albert Einstein to illustrate what Schrödinger saw as the problems of the Copenhagen interpretation of quantum mechanics. In the thought experiment, a hypothetical cat may be considered simultaneously both alive and dead, while it is unobserved in a closed box, as a result of its fate being linked to a random subatomic event that may or may not occur. In quantum mechanics, Schrödinger's cat is a thought experiment that illustrates a paradox of quantum superposition.

As illustrated, the objects are in a state of superposition: the cat is both alive and dead.

Schrödinger's cat: a cat, a flask of poison, and a radioactive source connected to a Geiger counter are placed in a sealed box. For other uses, see Schrödinger's cat (disambiguation).

Thought train apple