Optical Qubits and a Source-Checked Audit

Dual Rail Encodes Zero And One

physical path labels

An optical qubit basis can be taught as a checked upper-versus-lower rail label. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Logical zero occupies the upper rail

The basis binding for logical zero is upper count 1 and lower count 0.

∣0⟩rail:Nupper=1|0\rangle_{\text{rail}}:\quad N_{\text{upper}}=1
Dual rail zeroThe rail bars bind the logical value.1upper0lowerdual rail

Logical one occupies the lower rail

The basis binding for logical one is upper count 0 and lower count 1.

∣1⟩rail:Nlower=1|1\rangle_{\text{rail}}:\quad N_{\text{lower}}=1
Dual rail oneThis is a basis label, not an analyzer claim.0upper1lowerdual rail