No one denies that when a measurement is performed, the measuring system and the measured system become entangled (and the aggregate system containing both continues evolving unitarily).<p>&gt; When you &quot;measure&quot; the two halves of an EPR pair what you are really doing is performing two measurements on whatever system produced the EPR pair to begin with.<p>Here&#x27;s the problem with that.  Consider the measurements of a pair of space-like separated entangled photons.  A <i>choice</i> can be made about the details of these measurements by the experimenters at the last second possible.  For example, the rotation angle of a polarizer can be randomly chosen the instant before a photon strikes it, yet correlations with this choice show up in the <i>other</i> measurement that was taken far away.  (Note that these correlations still don&#x27;t allow you to send information faster than light.)  But the &quot;which angle&quot; information was never contained in whatever system produced the two photons.