Correlating Space and Time: "Homodyning is a process that involves a known reference laser, called the local oscillator, to measure the statistical properties of an unknown field: Shchukin explains to PhysOrg.com: “Appropriately analyzing the measured data allows us to determine the moments of the radiation field. Knowing the moments (which completely describe a radiation field) helps us to better understand other characteristics of quantum systems.”

The method Shchukin and Vogel propose, called balanced homodyne correlation (BHC) technique, has an advantage in that it uses simpler reconstruction procedure for arbitrary space-time correlations. Using an appropriate number of beam splitters and photo-detectors would allow scientists to measure, in principle, the correlations of an arbitrarily high order. This method goes beyond mere homodyne detection into correlation—offering something that can be experimentally applied.

“To my knowledge,” Shchukin says, “this is the first approach to experimentally realize such a general correlation measurement.” "