NIST scientists are reporting a new detection scheme that reportedly can get up to 99% efficiency.
Using essentially the same technology that permitted them to achieve 88 percent detection efficiency five years ago,** the team has enhanced its ability to detect photons largely by improving the alignment of the detector and the optical fibers that guide photons into it. The basic principle of the detector is to use a superconductor as an ultra-sensitive thermometer. Each individual photon hitting the detector raises the temperature—and increases electrical resistance—by a minute amount, which the instrument registers as the presence of a photon.
According to team member Sae Woo Nam, the advantage of this type of single photon detector is that the new detector design not only measures lower levels of light than have ever been possible, but does so with great accuracy.
I wonder if such a detector can be employed in the Bell-type experiments. This type of efficiency can greatly reduce the background subtraction and also lay to rest the detection loophole argument.