  Quantum circuit depth minimization is critical for practical applications of
circuit-based quantum computation. In this work, we present a systematic
procedure to decompose multiqubit controlled unitary gates, which is essential
in many quantum algorithms, to controlled-NOT and single-qubit gates with which
the quantum circuit depth only increases linearly with the number of control
qubits. Our algorithm does not require any ancillary qubits and achieves a
quadratic reduction of the circuit depth against known methods. We show the
advantage of our algorithm with proof-of-principle experiments on the IBM
quantum cloud platform.
