Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Correlated Photon Based Metrology Without Absolute Standards



Alan L. Migdall


Pairs of photons produced two at a time via optical parametric down-conversion have proved to be a useful tool for metrology. The status of three such applications is presented. One common theme through each of these applications is that they offer absolute results without any externally calibrated standards.
Physics Today


correlated photon, down-conversion, metrology, polarization mode dispersion, quantum efficiency, radiance
Created January 1, 1999, Updated February 17, 2017