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Single-Photon Mach-Zehnder Interferometer

Fire single photons through a Mach-Zehnder interferometer one at a time and watch an interference pattern build up detector by detector as you sweep the relative phase between the two arms. Switch on a which-path detector and watch the same pattern flatten into an uncorrelated 50/50 split — a live demonstration of complementarity.

Quantum Physics3DModerate60 FPS🔥 Fire

Fire individual photons through a simulated Mach-Zehnder interferometer and watch detection events accumulate at two output ports as you sweep the relative phase between its arms. With no which-path detector, the accumulated click fraction traces a smooth interference fringe — each photon interferes with itself. Switch on the which-path detector in arm A and the same experiment's accumulated pattern collapses to a flat 50/50 split, demonstrating that extracting which-path information destroys the interference.

⚙ Under the hood

Fire single photons through a Mach-Zehnder interferometer one at a time and watch an interference pattern build up detector by detector as you sweep the relative phase between the two arms. Switch on a which-path detector and watch the same accumulated pattern flatten into an uncorrelated 50/50 split — a live demonstration of quantum complementarity.

Mach-ZehnderWhich-PathQuantum InterferenceComplementaritySingle PhotonWave-Particle DualityThree.js

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install