  where |ready&gt;AL (|ready&gt;AR) denotes the state of the L-apparatus (R-apparatus) being ready to measure z-spin. In this state, the L- and the R-apparatus are in the definite state of being ready to measure z-spin, and (similarly to the state |ψ9&gt;) the L- and the R-particle have definite z-spin properties: Either the L-particle has z-spin ‘up’ and the R-particle has z-spin ‘down,’ or the L-particle has z-spin ‘down’ and the R-particle has z-spin  ‘up,’[24]   where the probability of the realization of each of these possibilities is approximately 1/2. In the (earlier) z-spin measurement on the L-particle, the state of the particle pair and the apparatuses evolves to the state: