  Here we report on the production and tomography of genuinely entangled
Greenberger-Horne-Zeilinger states with up to 10 qubits connecting to a bus
resonator in a superconducting circuit, where the resonator-mediated
qubit-qubit interactions are used to controllably entangle multiple qubits and
to operate on different pairs of qubits in parallel. The resulting 10-qubit
density matrix is unambiguously probed, with a fidelity of $0.668 \pm 0.025$.
Our results demonstrate the largest entanglement created so far in solid-state
architectures, and pave the way to large-scale quantum computation.
