Interpreting detector states in Zeilinger's four-detector interferometry setup

[naima]

Hi all,

I am reading this Zeilinger http://www.univie.ac.at/qfp/publications3/pdffiles/1996-04.pdf
Look at fig 1. There are four detectors D1 D2 D3 and D4.
When one of these detectors click, what does it mean? what is the state it detects?

The author gives a formula in the first page. P13 = (1 + cos x)/2.
how can we get it and what is the state D1 tensor D3?
Thanks.

 

[forcefield]

Look at fig 1. There are four detectors D1 D2 D3 and D4.
When one of these detectors click, what does it mean? what is the state it detects?

I don't know if there is a click but from the output of a detector you can tell that one or more photons were absorbed by the detector.

The author gives a formula in the first page. P13 = (1 + cos x)/2.
how can we get it

They can get it by doing the experiment. I don't know if there is a theory where it can be derived from.

what is the state D1 tensor D3?

Detection by both D1 and D3. I'm not sure if ^ denotes tensor in the paper.