Quantum mechanics has an exciting feature: a single event can exist in a state of superposition – happening bothhereandthere, or bothtodayandtomorrow.

Such superposition is quite challenging to create as they are easily destroyed if any information about the event’s place and time leaks into the surrounding – and even if nobody records this information. Once superposition is created, they lead to observations that are very different from that of classical physics, questioning down to our very understanding of space and time.

Recently scientists from EPFL, MIT, and CEA Saclay demonstrate a state of vibration simultaneously at two different times. They evidence this quantum superposition by measuring the strongest class of quantum correlations between light beams that interact with the vibration.