这是Scheme of a "two-channel" Bell test
The source S produces pairs of "photons", sent in opposite directions. Each photon encounters a two-channel polariser whose orientation can be set by the experimenter. Emerging signals from each channel are detected and coincidences counted by the coincidence monitor CM.
S同时产生A光子与B光子。光子通过a或b时,偏极被侦测到。四种光子A+,A-,B+,B-经过CM记录抵达的时间。如果a距离S比b近,A光子抵达a时成为A+光子时,B光子应立即成为B-光子。A+光子与B-光子抵达CM的时间差应该是固定。同样A-光子与B+光子抵达CM的时间差也应该是固定。
问题是实验如何证明同时性?