Coherence time

The early boxes are still sharp enough for the cancellations you meant to run. Further along the row the boxes go dim, because a circuit that runs on toward the coherence time of the device loses more of its phase.

Coherence time is the typical time a particular qubit keeps its relative phase before noise fades it. Circuits much shorter than that run cleanly, and longer ones lose their cancellations. It is read off one chip or one trap, and it is why a long calculation is drawn with many physical qubits protecting each result you intend to trust.

The fading is gradual rather than a cliff, and the machine keeps printing bits as the cancellations go muddy. Keith would prefer the number to be a constant of the subject. The papers publish it per device, and Malcolm files them that way.

Coherence time

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