Applications and tests

The experiment as described is a purely theoretical one, and the machine proposed is not known to have been constructed. However, successful experiments involving similar principles, e.g. superpositions of relatively large (by the standards of quantum physics) objects have been performed.[33][better source needed] These experiments do not show that a cat-sized object can be superposed, but the known upper limit on "cat states" has been pushed upwards by them. In many cases the state is short-lived, even when cooled to near absolute zero.

• A "cat state" has been achieved with photons.[34]
• A beryllium ion has been trapped in a superposed state.[35]
• An experiment involving a superconducting quantum interference device ("SQUID") has been linked to the theme of the thought experiment: "The superposition state does not correspond to a billion electrons flowing one way and a billion others flowing the other way. Superconducting electrons move en masse. All the superconducting electrons in the SQUID flow both ways around the loop at once when they are in the Schrödinger's cat state."[36]
• A piezoelectric "tuning fork" has been constructed, which can be placed into a superposition of vibrating and non vibrating states. The resonator comprises about 10 trillion atoms.[37]

An experiment involving a flu virus has been proposed.[38]

An experiment involving a bacterium and an electromechanical oscillator has been proposed.[39]

In quantum computing the phrase "cat state" sometimes refers to the GHZ state, wherein several qubits are in an equal superposition of all being 0 and all being 1; e.g.,

|ψ⟩=12(|00…0⟩+|11…1⟩).

According to at least one proposal, it may be possible to determine the state of the cat before observing it.[40][41]

Extensions

• In August 2020, physicists presented studies involving interpretations of quantum mechanics that are related to the Schrödinger's cat and Wigner's friend paradoxes, resulting in conclusions that challenge seemingly established assumptions about reality.[42][43][44]

Schrödinger's cat quantum superposition of states and effect of the environment through decoherence

See also

• Basis function
• Cat state
• Complementarity (physics)
• Double-slit experiment
• Elitzur–Vaidman bomb tester
• Heisenberg cut
• Modal realism
• Observer effect (physics)
• Ray cat
• Schroedinbug
• Schrödinger's cat in popular culture

References

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External Links

• A spoken word version of this article (created from a revision of the article dated 2013-08-12).
• Schrödinger's Cat from the Information Philosopher.
• Schrödinger's Cat - Sixty Symbols - a video published by the University of Nottingham.
• Schrödinger's Cat - a podcast produced by Sift.