Multiqubit gates for superconducting qubits

Superconducting qubits are a leading platform for quantum computing, offering substantial flexibility in designing qubits and gate operations. The standard approach relies on repeatedly applying single- and two-qubit gates to construct arbitrary quantum circuits. Here, we propose an alternative strategy based on multiqubit entangling gates between superconducting qubits. Specifically, we derive analytic forms of three-qubit gates in a transmon system and demonstrate their use in test circuits to generate entangled states such as GHZ (Greenberger–Horne–Zeilinger) and W states, as well as to implement standard three-qubit logic gates including Toffoli, iToffoli, and Fredkin gates. We analyze both triangular and linear qubit configurations, numerically optimizing the control parameters of the three-qubit and single-qubit gates to achieve high-fidelity circuit implementations. Our results show that employing multiqubit gates can substantially reduce the number of steps required to realize target circuits compared to the conventional single- and two-qubit gate approach.