OPTICAL EXPERIMENTS ILLUSTRATING THE SIGNIFICANCE OF THE BEIL INEQUATITIES

Recently the possibility of generating squeezed states of light has provided for an important new tool in studying questions that are of crucial importance for the foundations of quantum mechanics. Squeezed states, being states of the electromagnetic field without a classical analogue, seem particularly suited for studying effects that are typically quantum mechanical. For this reason it is not surprising that they have been applied in tests of the Heisenberg uncertainty relationl and of the Bell inequalities (BI)2. In the latter experiment, which was performed by Ou and Mandel2, the two-photon character of squeezed states generated in parametric downconversion is used in order to obtain a correlated state of the electromagnetic field violating the BI. This was verified in Einstein-Podolsky-Rosen (EPR)-like experiments in which the joint probability P{01,0) was measured of one photon being polarized in the direction d1 and the other one in the direction 02. In order to test the BI the experiment was repeated for differen