To carry out the experiment, the ANU team initially trapped a collection of helium atoms in a Bose-Einstein condensate (a medium in which a dilute gas is cooled to temperatures very close to absolute zero), and then forcibly ejected them from their containment until there was only a single atom left behind.
This remaining atom was then released to pass through a pair of counter-propagating laser beams (that is, beams moving in opposite directions), which created a pattern to act as a crossroads for the atom in the same way that a solid diffusion grating would act to scatter light.
After this, another laser-generated grating was randomly added and used to recombine the routes offered to the atom. This second grating then indiscriminately produced either constructive or destructive interference as if the atom had journeyed on both paths. Conversely, when the second light grating was not randomly added, no interference would be introduced, and the atom would behave as if it had followed only one path.
However, and this is the really weird part, the arbitrary number generated to determine if the grating was added or not was only generated after the atom had passed through the crossroads. But, when the atom was measured at the end of its path – before the random number was generated – it already displayed the wave or particle characteristics applied by the grating after it had completed its journey.
According to Truscott, this means that if one chooses to believe that the atom really did take a particular path or paths, then one also has to accept that a future measurement is affecting the atom's past.
"The atoms did not travel from A to B. It was only when they were measured at the end of the journey that their wave-like or particle-like behavior was brought into existence," said Truscott. "It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it.”