Linear-depth quantum circuits for multiqubit controlled gates

TL;DR

This paper introduces a systematic method to decompose multiqubit controlled gates into simpler gates, significantly reducing circuit depth without ancillary qubits, enhancing the practicality of quantum algorithms.

Contribution

The authors present a depth-minimizing decomposition algorithm for multiqubit controlled gates that scales linearly and requires no ancillary qubits, outperforming existing methods.

Findings

Circuit depth reduces quadratically compared to prior methods

Algorithm requires no ancillary qubits

Experimental validation on IBM quantum platform

Abstract

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.