  While all quantum algorithms can be expressed in terms of single-qubit and
two-qubit gates, more expressive gate sets can help reduce the algorithmic
depth. This is important in the presence of gate errors, especially those due
to decoherence. Using superconducting qubits, we have implemented a three-qubit
gate by simultaneously applying two-qubit operations, thereby realizing a
three-body interaction. This method straightforwardly extends to other quantum
hardware architectures, requires only a "firmware" upgrade to implement, and is
faster than its constituent two-qubit gates. The three-qubit gate represents an
entire family of operations, creating flexibility in quantum-circuit
compilation. We demonstrate a gate fidelity of $97.90\%$, which is near the
coherence limit of our device. We then generate two classes of entangled
states, the GHZ and W states, by applying the new gate only once; in
comparison, decompositions into the standard gate set would have a two-qubit
gate depth of two and three, respectively. Finally, we combine characterization
methods and analyze the experimental and statistical errors on the fidelity of
the gates and of the target states.
