  Quantum entanglement is a fundamental property of coherent quantum states and
an essential resource for quantum computing. While two-qubit entanglement has
been demonstrated for spins in silicon, creation of multipartite entanglement,
a first step toward implementing quantum error correction, has remained
challenging due to the difficulties in controlling a multi-qubit array, such as
device disorder, magnetic and electrical noises and exacting exchange controls.
Here, we show operation of a fully functional three-qubit array in silicon and
generation of a three-qubit Greenberger-Horne-Zeilinger (GHZ) state. We obtain
a state fidelity of 88.0 percent by quantum state tomography, which witnesses a
genuine GHZ-class quantum entanglement that is not biseparable. Our result
shows the potential of silicon-based qubit platform for demonstrations of
multiqubit quantum algorithms.
