Programmable Superconducting Processor with Native Three-Qubit Gates

Superconducting circuits are at the forefront of quantum-computing technology because of the unparalleled combination of good coherence, fast gates, and flexibility in design parameters. The majority of experiments demonstrating small quantum algorithms in the superconducting architecture have used transmon qubits, which are coupled via capacitors or microwave cavities. Apart from coherence and gate fidelity, two important factors that currently limit the performance of a superconducting processor are nearest-neighbor interqubit coupling (in one or two dimensions) and being restricted to two-qubit entangling gates only. In this work, we present a programmable three-qubit processor circuit, nicknamed "trimon," with strong all-to-all coupling and access to native three-qubit gates. We benchmark our processor by implementing a three-qubit version of various algorithms, namely Deutsch-Jozsa, Bernstein-Vazirani, Grover's search and the quantum Fourier transform. In particular, we note that the native three-qubit controlled operations enable our ancilla-free implementation of Grover's algorithm to outperform previous demonstrations. Our results clearly show the advantage of having native three-qubit gates, and that can play a crucial role in improving the performance of larger systems having the trimon as a building block.