Quest for Entropy · the toy, by hand
One photon, Wheeler's interferometer, the table of the last episode. The run is a conveyor: the photon moves down through the stations, and the whole run is always shown. Tables are on the left and what happens is on the right. In the middle, each station shows its quantum-computer operation in brackets. Each station also has dials to play with. Every change reruns everything below it, and the counts too. The defaults are the real experiment; reload the page to get them back. The marker M has a switch on its own station: switch it off and its stations grey out.
Every line is the same kind of number: the share of photons whose D1 said 0 (detector 0), inside one group. Solid lines with dots are counted, one signed fact per photon. Dashed lines are the key: |arrow|² read off the table, with no counting. The groups are made afterwards, by D2's answer (M's reader); no photon changes group or detector.
Not claimed: that the toy explains the arrows. The turns, the delay and the meetings are standard quantum arithmetic, imported as in the last episode, and every count on this page is the one quantum mechanics predicts. What the page shows is that a ledger on which a meeting is only a promise needs no photon that waits and no message to the past. The toy is told where the settlements happen: at D1, and at D2. On the brackets: the toy's turn with dial θ is RX(−2θ). At 45° it does the job of H in the circuit (a beam splitter), up to the i that the toy's turn carries.