In quantum mechanics, wave function collapse (also called collapse of the state vector or reduction of the wave packet) is the phenomenon in which a wave function—initially in a superposition of several different possible eigenstates—appears to reduce to a single one of those states after interaction with an observer. In simplified terms, it is the reduction of the physical possibilities into a single possibility as seen by an observer. It is one of two processes by which quantum systems evolve in time, according to the laws of quantum mechanics as presented by John von Neumann. The reality of wave function collapse has always been debated, i.e., whether it is a fundamental physical phenomenon in its own right or just an epiphenomenon of another process, such as quantum decoherence. In recent decades the quantum decoherence view has gained popularity and is commonly taught at the graduate level (e.g. Cohen-Tannoudji's standard textbook). Collapse may be understood as an update in a probabilistic model, given the observed result. The quantum filtering approach and the introduction of quantum causality non-demolition principle allowed for a derivation of quantum collapse from the stochastic Schrödinger equation.
Other articles related to "wave function collapse, collapse, wave function, wave function collapses, wave, wave functions":
... The concept of wavefunction collapse was introduced by Werner Heisenberg in his 1927 paper on the uncertainty principle, "Über den anschaulichen Inhalt der quantentheoretischen Kinematic ... postulated that there were two processes of wave function change The probabilistic, non-unitary, non-local, discontinuous change brought about by observation and measurement, as outlined above ... However, when the wave function collapses (process (1)), from an observer's perspective the state seems to "leap" or "jump" to just one of the basis states and uniquely acquire the value of the property being measured ...
... Penrose's idea is a type of objective collapse theory ... For these theories, the wavefunction is a physical wave, which experiences wave function collapse as a physical process, with observers not having any special role ... Penrose theorises that the wave function cannot be sustained in superposition beyond a certain energy difference between the quantum states ...
... equation, which is time-symmetric, and by wave function collapse, which is time irreversible ... As the mechanism of wave function collapse is philosophically obscure, it is not completely clear how this arrow links to the others ... amounts to an observation that nature shows a bias for collapsing wave functions into higher entropy states versus lower ones, and the claim that this is ...
... Wave function collapse is a forced term for whatever happened when it becomes appropriate to replace the description of an uncertain state of a system by a description of the system ... However, the photon has disappeared, and the wave function has disappeared with it ...
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