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Contrary to popular belief, Schrödinger did not intend this thought experiment to indicate that he believed that the dead-alive cat would actually exist; rather he considered the quantum mechanical theory to be incomplete and not representative of reality in this case. Since a cat clearly must either be alive or dead (there is no state between alive and dead) surely the same must be true of the nucleus. It must be either decayed or not decayed.
The original article appeared in the German magazine Naturwissenschaften ("Natural Sciences") in 1935: E. Schrödinger: "Die gegenwärtige Situation in der Quantenmechanik" ("The present situation in quantum mechanics"), Naturwissenschaften, 48, 807, 49, 823, 50, 844 (November 1935). It was intended as a discussion of the EPR article published by Einstein, Podolsky and Rosen in the same year. Apart from introducing the cat, Schrödinger also coined the term " entanglement" (German: Verschränkung) in his article.
In the Copenhagen interpretation, a system stops being a mixture of states and becomes either one or the other when an observation takes place. This experiment makes apparent the fact that the nature of measurement, or observation, is not well defined in this interpretation. Some interpret the experiment to mean that while the box is closed, the system simultaneously exists in a mixed superposition of the states "decayed nucleus/dead cat" and "undecayed nucleus/living cat", and that only when the box is opened and an observation performed does the wave function collapse into one of the two states. More intuitively, some feel that the "observation" is taken when a particle from the nucleus hits the detector. However (and this is a key point of the thought experiment), there isn't any rule within the Copenhagen interpretation that says one way or the other, and this interpretation of quantum mechanics is incomplete without such rules and explanations for how such rules come to exist.
In the Everett many-worlds interpretation, which does not single out observation as a special process, both states persist, but decohere. When an observer opens the box, he becomes entangled with the cat, so observer-states corresponding to the cat being alive and dead are formed, and each can have no interaction with the other.
Curiously, all of this has some practical use in quantum cryptography. It is possible to send light that is in a superposition of states down a fiber optic cable. Placing a wiretap in the middle of the cable which intercepts and retransmits the transmission will collapse the wavefunction (in the Copenhagen interpretation, "perform an observation") and cause the light to fall into one state or another. By performing statistical tests on the light received at the other end of the cable, one can tell whether it remains in the superposition of states or has already been observed and retransmitted. In principle, this allows the development of communication systems that cannot be tapped without being noticed at the other end. This experiment (which can be performed, though a workable quantum cryptographic communications system which can transmit large quantities of data has not yet been constructed) also illustrates that "observation" in the Copenhagen interpretation has nothing to do with consciousness, in that a perfectly unconscious wiretap will cause the statistics at the end of the wire to be different.
An interesting variant of the Schrödinger's Cat experiment known as the
quantum suicide machine has been proposed by cosmologist Max TegmarkMax Tegmark born in Sweden, is a cosmologist formerly at the University of Pennsylvania but now at the Massachusetts Institute of Technology. He is one of the proponents of the quantum suicide thought-experiment, and has come up with a nice mathematical a.It asks the question, what does the Schrödinger's Cat experiment look like from the point of view of the cat, and argues that this question may be able to distinguish between the Copenhagen interpretation and many worlds. Another variant on the experiment is Wigner's friendWigner's friend is a thought experiment proposed by the physicist Eugene Wigner; it is an extension of the Schrodinger's cat experiment designed as a point of departure for discussing the mind-body problem as viewed by the Copenhagen interpretation of qua.
Physicist Stephen HawkingReuters/Stephen Hird Stephen William Hawking, CH CBE FRS (born January 8 1942) is one of the world's leading theoretical physicists. Hawking is Lucasian professor of mathematics at the University of Cambridge (a post once held by Isaac Newton). Biography once exclaimed, "When I hear of Schrödinger's cat, I reach for my gun," paraphrasing Hermann GöringHermann Wilhelm Goring (also spelled Hermann Goering in English) ( January 12, 1893 — October 15, 1946) was a prominent and early member of the Nazi party, founder of the Gestapo, and one of the main architects of Nazi Germany. He is often quoted from the's anti-intellectual quote, "When I hear the word 'culture', I reach for my revolver", which Göring quoted from a playA play (noun) is a common literary form, usually consisting chiefly of dialog between characters, and usually intended for performance rather than reading. However, many scholars study plays in this more academic manner, particularly classical plays such by GermanThe Federal Republic of Germany ( German: Bundesrepublik Deutschland is one of the world's leading industrialized countries, located in the middle of the European Union. It is bordered to the north by the North Sea, Denmark and the Baltic Sea, to the east playwright and Nazi Poet LaureatePoet Laureate is a poet officially appointed by a government and often expected to compose poems for state occasions and other government events. In the United Kingdom, it has over the centuries come to be the title of the official poet of the British mon, Hanns Johst.