  We design a circuit structure with linear depth to implement an $n$-qubit
Toffoli gate. The proposed construction uses a quadratic-size circuit consists
of elementary 2-qubit controlled-rotation gates around the x axis and uses no
ancilla qubit. Circuit depth remains linear in quantum technologies with
finite-distance interactions between qubits. The suggested construction is
related to the long-standing construction by Barenco et al. (Phys. Rev. A, 52:
3457-3467, 1995, arXiv:quant-ph/9503016), which uses a quadratic-size,
quadratic-depth quantum circuit for an $n$-qubit Toffoli gate.
