This is the 2D hydrodynamic analog of the double-slit experiment (after Couder & Fort's walking-droplet experiments), not the photon/electron version. A droplet bounces on a vibrating bath and, on every bounce, re-excites the standing Faraday wave it is already riding — the droplet is a real particle with a definite trajectory at all times, but a "pilot wave" it generates steers it. That is a direct hydrodynamic analog of de Broglie–Bohm pilot-wave mechanics.
Each droplet is launched with a random lateral offset and travels straight until it reaches the barrier. If it is not aligned with slit A or slit B it is absorbed; otherwise it passes through exactly one slit — a single, definite path. From that instant the guiding field is the coherent sum of two wavelets radiating from slit A and slit B (Huygens' principle):
- Z(x,y) = A/√dA · eikdA + B/√dB · eikdB — the combined complex wave from both slits, evaluated at every point downstream.
- v ∝ ∇arg(Z) — the droplet's velocity is driven by the local gradient of the wave's phase, the same guidance equation used for genuine Bohmian trajectories. Trajectories bend toward intensity maxima and never cross a nodal line.
No single droplet ever "sees" both slits' interference directly — each one only feels the local wave gradient along its own path. Yet because every droplet's guiding field is the true two-slit sum, launching many droplets at random offsets makes their landing points pile up into the classic fringe pattern on the screen, exactly as in the real Couder–Fort experiments and in Bohmian trajectory calculations for the quantum case. The "wave memory" slider blends this guided velocity with plain straight-line motion, mimicking how a decaying (low-memory) Faraday wave field washes the fringes out.