Violation of Bell’s inequality by macroscopic states generated via parametric down-conversion

We show that correlated photon-number states predicted to violate a Bell’s inequality of the Clauser-Horne-Shimony-Holt type might be generated from parametric amplification. The test is potentially one of macroscopic quantum mechanics in that violations are predicted for situations where a large number of photons are detected in a single detector at one time. The traditional amplifier and detectors allow violation only for regimes where the probability of generation of a macroscopic state is very small. We suggest that this probability may be dramatically improved with the use of squeezing and photon-number-state-preparation techniques.