Circuit depth

QPU137 computes depth by ASAP (as-soon-as-possible) layering over the operation dependency graph: each operation occupies one layer on every qubit it touches; barriers force a boundary but add no depth. We always report two-qubit depth alongside total depth — layers containing at least one entangling operation — because on current hardware that is the number that actually predicts fidelity.

Depth is a computed property, but conventions differ: some tools count only entangling layers, some count every scheduling step, and compiled depth depends on which basis the counting happens in (logical gates vs native operations after transpilation — see the compilation comparison).

Never compare a logical depth to a compiled depth, or depths counted in different gate bases: the same circuit can honestly be "depth 8" and "depth 31" depending on when you count. QPU137 states its definition (above) and applies it uniformly; vendor-published depths may follow other conventions, and our records say when the convention is unknown.