Direct Implementation of High-Fidelity Three-Qubit Gates and Quantum Simulation

Three-qubit gates can be constructed using combinations of single-qubit and two-qubit gates, making their
independent realization unnecessary. However, direct implementation of three-qubit gates reduces the depth
of quantum circuits, streamlines quantum programming, and facilitates efficient circuit optimization, thereby
enhancing overall performance in quantum computation. In this work, we propose and experimentally
demonstrate a high-fidelity scheme for implementing a three-qubit controlled-controlled-Z (CCZ) gate in a
flip-chip superconducting quantum processor with tunable couplers. As a showcase, we
utilize the CCZ gate as an oracle to implement the Grover search algorithm on three qubits, demonstrating high
performance with the target probability amplitude significantly enhanced after two iterations. Recent quantum simulation results will also be presented.