This article is very misleading, which is typical of QM material of this era (early 90s). > Strange as it may sound, interference can only occur when no one is

This article is very misleading, which is typical of QM material of this era (early 90s). > Strange as it may sound, interference can only occur when no one is watching. This is not true. The correct statement is that interference only manifest itself in isolated systems, i.e. systems that are not entangled with anything outside of themselves. Systems that are being "measured" or "watched" are entangled, but they are not the only such systems. Any entanglement outside of the system under consideration is enough to stop interference effects from manifesting themselves. The reason I say "outside of the system under consideration" is because the ability to observe interference depends on where you draw the line between the system you are measuring and everything else. For example, in an EPR pair you can choose to either consider a single member of the pair, in which case you cannot observe any interference, or you can consider the pair as a whole, in which case you can.