I was watching a MIT opencourseware video on quantum mechanics. The first video is on superposition. The link is here: http://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2013/lecture-videos/lecture-1/ In short the lecture shows a series of experiments done on electron spin in the X, Y or Z plane. He refers to them as 'Hardness' and 'Colour', which I am assuming refers to up and down spin in the Y axis and and left and right spin in the x axis for example. Anyway, one of the experiments (around 47 mins in) takes electrons of a know spin state, (e.g. 'Up' in the Y axis) and puts them through a device that tests for a different spin axis (e.g. left and right in the X axis). Depending on the what spin is detected the electron can take either of two paths, which then merge via the use of mirrors before the electron enters a final device that tests for the original spin state (e.g. Up and down in the Y axis) The expected results are that the final device should detect 50% of the electrons in either the up or down state, but instead the results are 100% 'Up' spin state for example. However by blocking off one of the paths and repeating the experiment, the results change to 50% up and 50% down. The lecture shows that the electron couldn't have taken the 'left' path, it couldn't have taken the 'right' path and it couldn't have taken both paths so it exists in a state of superposition. My question.... Is possible that the wave / particle nature of an electron plays a part in this outcome? So the 'particle' part of the electron may take one path, but the 'wave' part of the electron takes the other and so it interferes on itself. Hence the strange result. And when blocking one of the paths, this doesn't happen so the outcome is what may be expected when running the experiment with two devices in series without the mirrors?