No-go theorem

About: No-go theorem is a research topic. Over the lifetime, 1753 publications have been published within this topic receiving 54488 citations.

Quantum cryptography based on Bell's theorem.

Abstract: Practical application of the generalized Bells theorem in the so-called key distribution process in cryptography is reported. The proposed scheme is based on the Bohms version of the Einstein-Podolsky-Rosen gedanken experiment and Bells theorem is used to test for eavesdropping. © 1991 The American Physical Society.

The fluctuation-dissipation theorem

Abstract: The linear response theory has given a general proof of the fluctuation-dissipation theorem which states that the linear response of a given system to an external perturbation is expressed in terms of fluctuation properties of the system in thermal equilibrium. This theorem may be represented by a stochastic equation describing the fluctuation, which is a generalization of the familiar Langevin equation in the classical theory of Brownian motion. In this generalized equation the friction force becomes retarded or frequency-dependent and the random force is no more white. They are related to each other by a generalized Nyquist theorem which is in fact another expression of the fluctuation-dissipation theorem. This point of view can be applied to a wide class of irreversible process including collective modes in many-particle systems as has already been shown by Mori. As an illustrative example, the density response problem is briefly discussed.

Experimental Tests of Realistic Local Theories via Bell's Theorem

Abstract: We have measured the linear polarization correlation of the photons emitted in a radiative atomic cascade of calcium A high-efficiency source provided an improved statistical accuracy and an ability to perform new tests Our results, in excellent agreement with the quantum mechanical predictions, strongly violate the generalized Bell's inequalities, and rule out the whole class of realistic local theories No significant change in results was observed with source-polarizer separations of up to 65 m

Zeno's paradox in quantum theory

Abstract: A quantum-theoretic expression is sought for the probability that an unstable particle prepared initially in a well-defined state will be found to decay sometime during a given interval. It is argued that probabilities like this which pertain to continuous monitoring possess operational meaning. A simple natural approach to this problem leads to the startling conclusion that an unstable particle which is continuously observed whether it decays will never be found to decay. Since recording the track of an unstable particle (which can be distinguished from its decay products) realizes such continuous observations to a close degree of approximation, the above conclusion poses a paradox which we call Zeno's Paradox in Quantum Theory. Its implications and possible resolutions are briefly discussed. The mathematical transcription of the above-mentioned conclusion is a structure theorem concerning semigroups. Although special cases of this theorem are known, the general formulation and the proof given here are believed to be new. The known ''no-go'' theorem concerning the semigroup law for the reduced evolution of any physical system (including decaying systems) is subsumed under the theorem as a direct corollary.

Going Beyond Bell’s Theorem

Abstract: Bell’s Theorem proved that one cannot in general reproduce the results of quantum theory with a classical, deterministic local model. However, Einstein originally considered the case where one could define an “element of reality”, namely for the much simpler case where one could predict with certainty a definite outcome for an experiment For this simple case, Bell’s Theorem says nothing. But by using a slightly more complicated model than Bell, one can show that even in this simple case where one can make definite predictions, one still cannot generally introduce deterministic, local models to explain the results.