“For the first time ever, we kind of have a time-traveling machine going in both directions,” said Sonja Franke-Arnold, a quantum physicist at the University of Glasgow in Scotland who was not involved in the research.

After the player arranges the gadgets and other optical elements however they want, they send a photon through the maze, perhaps splitting it into a superposition of two paths using a half-silvered mirror.

Only when the photon experiences a superposition that takes it forward and backward through both gadgets — a tactic dubbed the “quantum time flip” — can the player theoretically win every round.

Both teams shattered the theoretical 90% limit, proving that their photons experienced a superposition of two opposing transformations and hence an indefinite arrow of time.

Granted, he admits, the circuit can time-flip only photons undergoing polarization changes; if space-time were truly in a superposition, dueling time directions would affect everything.

“This allows you to do more things than just implementing the operations in one order or another,” said Cyril Branciard, a quantum information theorist at the Néel Institute in France.