Consider the following setup: The device at the center launches
a pair of particles in opposite directions. Each particle enters
an apparatus capable of performing one of three measurements.
Each measurement has two possible outcomes, which are indicated
by either a red or a green light. In each run of the experiment
the measurement performed is randomly selected for each
apparatus. After a large number of runs, we have in our hands a
long record of apparatus settings and responses. Like this one:
21RG 31GG 12RG 13GR 31GR 12RG 22GR 21GG 11RG 31RR 33GR 31RG 21RR
33GR 11GR 31GG 13GG 22RG 12RG 32GR 31GG 22RG 11GR 12GG 23RR 22RG
23GG 32RG 23RG … Any such record displays the following
characteristics (how these statistical properties can actually
be obtained is explained on this page): - Whenever both
apparatuses perform the same measurement (settings 11, 22, or
33), equal colors (RR or GG) are never observed. This means
that, if the settings agree, the outcomes are correlated: the
joint probability p(R & R), whic