  The family of $n$-bit Toffoli gates, with the two-bit Toffoli gate as the
figurehead, are of great interest in quantum information as they can be used as
universal gates and in quantum error correction, among other things. We present
a single-step implementation of arbitrary $n$-bit Toffoli gates (up to a local
change of basis), based on resonantly driving a single qubit that has a strong
Ising coupling to $n$ other qubits. The setup in the two-qubit case turns out
to be identical to the universal Barenco gate. The gate time and error are, in
theory, independent of the number of control qubits, scaling better than
conventional circuit decompositions. We note that our assumptions, namely
strongly coupling $n+1$ qubits and a driving frequency that scales with $n$,
may break down for large systems. Still, our protocol could enhance the
capabilities of intermediate scale quantum computers, and we discuss the
prospects of implementing our protocol on trapped ions, Rydberg atoms, and on
superconducting circuits. Simulations of the latter platform show that the
Toffoli gate with two control bits attains fidelities of above 0.98 even in the
presence of decoherence. We also show how similar ideas can be used to make a
series of controlled-\textsc{not}-gates in a single step. We show how these can
speed up the implementation of quantum error correcting codes and we simulate
the encoding steps of the three-qubit bit-flip code and the seven-qubit Steane
code.
