The photon enters as a wave and takes every path at once. Where paths recombine, their amplitudes add as arrows — line them up and the port glows; point them opposite and it goes completely dark.
Tap the phase shifters to rotate each path. Make every ☢ mine detector go dark and send the photon out the safe port.
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Ports dark
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All five solved
You tuned five interferometers to darkness — probabilities that cancel, something no classical particle can do. That's real quantum interference.
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How it works
A single photon enters at the source and flows along the rails. A beam splitter (the ✕ couplers) sends it two ways at once — it travels both arms as a wave of probability amplitude, which carries a phase (an arrow direction) as well as a size.
A phase shifter rotates the arrow on its rail. Tap to turn it by 45°. When two arms meet again at a splitter, their arrows add tip-to-tail: aligned arrows reinforce (bright), opposite arrows cancel to nothing (a dark port).
Your job: tune the shifters so every ☢ mine detector is dark. The panel at the bottom shows each detector's arrows adding up, so you can see the cancellation happen. Classical balls can only pile up — they can't subtract. Here, adding a path can make a detector less likely. Solve all five.