  We report the preparation and verification of a genuine 12-qubit entanglement
in a superconducting processor. The processor that we designed and fabricated
has qubits lying on a 1D chain with relaxation times ranging from 29.6 to 54.6
$\mu$s. The fidelity of the 12-qubit entanglement was measured to be above
$0.5544\pm0.0025$, exceeding the genuine multipartite entanglement threshold by
21 statistical standard deviations. Our entangling circuit to generate linear
cluster states is depth-invariant in the number of qubits and uses single- and
double-qubit gates instead of collective interactions. Our results are a
substantial step towards large-scale random circuit sampling and scalable
measurement-based quantum computing.
