GHZ-Experiment

The GHZ experiment, named after the physicists Greenberger, Horne and Zeilinger, is a ( thought ) experiment in quantum mechanics, with an important class of theories can be excluded with hidden variables. 1989 proposed Greenberger, Horne and Zeilinger before a state of three entangled particles, in contrast to the Bell 's inequalities satisfy four measurements in which to prove the correctness of quantum mechanics and to disprove the existence of hidden variables. After the instrumental possibilities were given, it was first time in 1999 conducted a similar experiment and the predictions of quantum mechanics are thereby confirmed.

Background

Two particles are created in an entangled state together and fly apart. These particles have only two possible states, and. Now, if the state of a particle is measured (for example ), one knows that the other particle is located in the other state ( ie ). Albert Einstein claimed that these properties of the particles were determined before, before you performed the measurements. Quantum mechanics describes these two particles as a single wave function, which makes both states are equally likely for both particles. Only by observing, by a measurement, it collapses the wave function, and depending on which state was measured with a particle, it is known then the exact state of the other particle.

Neither of these interpretations can be proved with only two entangled particles in an experiment. 1964 John Bell was but a system of inequalities ( Bell's inequality ) that an infinite number of measurements, a statistically exact solution to this dilemma supplies. Since an infinite number of measurements are virtually impossible to achieve, until the GHZ experiment allows an experimentally reasoned analysis or solution of this contradiction.