Certain nonclassical effects in four-wave mixing are studied within the framework of a quantum theory of multiwave mixing. It is shown that the Cauchy-Schwarz and Bell's inequalities are violated for large detuning of the pump frequency from the side-mode frequencies.
Output nonlocality and nonclassicality for the two modes are investigated in an entanglement laser system.Within the framework of a quantum theory of multiwave mixing, nonlocality and nonclassicality are discussed according to the violations of Bell inequality and Cauchy-Schwarz inequality.It is found that both nonlocality and nonclassicality can be fulfilled in the outside cavity fields under certain conditions.It is also shown that there are some nonclassical states that do not show nonlocality.
An optical field produced by intracavity four-wave mixing is shown to exhibit the following nonclassical features: photon antibunching, squeezing, and violation of Cauchy-Schwarz and Bell's inequalities. These intrinsic quantum mechanical effects are shown to be associated with the nonexistence of a positive normalizable Glauber-Sudarshan P function.
Output nonlocality and nonclassicality for the two modes are investigated in an entanglement laser sys-tem. Within the framework of a quantum theory of multiwave mixing,nonlocality and nonclassicality are discussed according to the violations of Bell inequality and Cauchy-Schwarz inequality. It is found that both nonlocality and nonclassicality can be fulfilled in the outside cavity fields under certain conditions. It is also shown that there are some nonclassical states that do not show nonlocality.
We have observed a violation of the Cauchy-Schwarz inequality in the macroscopic regime by more than 8 standard deviations. The violation has been obtained while filtering out only the low-frequency noise of the quantum-correlated beams that results from the technical noise of the laser used to generate them. We use bright intensity-difference squeezed beams produced by four-wave mixing as the source of the correlated fields. We also demonstrate that squeezing does not necessarily imply a violation of the Cauchy-Schwarz inequality.
The Cauchy-Schwarz (CS) inequality-one of the most widely used and important inequalities in mathematics-can be formulated as an upper bound to the strength of correlations between classically fluctuating quantities. Quantum-mechanical correlations can, however, exceed classical bounds. Here we realize four-wave mixing of atomic matter waves using colliding Bose-Einstein condensates, and demonstrate the violation of a multimode CS inequality for atom number correlations in opposite zones of the collision halo. The correlated atoms have large spatial separations and therefore open new opportunities for extending fundamental quantum-nonlocality tests to ensembles of massive particles.