The Mad new quantum experiment breaks the idea of ‘before’ and ‘after’

The Science Alert: For around a century it’s been thought that particles don’t have defined properties until we nail them down with a measurement.
That kind of quantum madness opens up a whole world of counter-intuitive paradoxes. Take this one, for example – it’s possible for a single particle to experience two sequences of events at the same time, making it impossible to know which came first.
Physicists from the University of Queensland designed a race course for light that forced a single particle to traverse two pathways at once, making it impossible to say in which order it completed a pair of operations.
In boring old everyday life you could roll a single ball down a ramp and have it ring bell A and then ring bell B. Or, if you’d prefer, you could roll it down another ramp and have it ring B before A.
If you want to get fancy you could even set up a rig so one bell causes the other bell to ring.
None of this is mind blowing, since we’re used to events in the Universe having a set order, where one thing precedes another in such a way that we presume an order of causation.
But nothing is so simple when we accept that reality is a blur of possibility prior to it being measured.
To demonstrate this, the physicists created a physical equivalent of something called a quantum switch, where multiple operations occur while a particle is in a superposition of all its possible locations.
Keeping it simple, the team set up a pathway that split apart and converged again in an interferometer, with access to each fork dependent on the polarisation of the light entering it.
Light waves travelling down each fork in the pathway would then merge and interfere to create a distinctive pattern depending on its properties.