High-Fidelity CZ Gates in Double Quantum Dot – Circuit QED Systems Beyond the Rotating-Wave Approximation

Semiconductor double quantum dot (DQD) qubits coupled via superconductingmicrowave resonators provide a powerful means of long-range manipulation of thequbits' spin and charge degrees of freedom. Quantum gates can be implemented byparametrically driving the qubits while their transition frequencies aredetuned from the resonator frequency. Long-range two-qubit CZ gates have beenproposed for the DQD spin qubit within the rotating-wave approximation (RWA).Rapid gates demand strong coupling, but RWA breaks down when coupling strengthsbecome significant relative to system frequencies. Therefore, understanding thedetrimental impact of time-dependent terms ignored by RWA is critical forhigh-fidelity operation. Here, we go beyond RWA to study CZ gate fidelity forboth DQD spin and charge qubits. We propose a novel parametric drive on thecharge qubit that produces fewer time-dependent terms and show that itoutperforms its spin counterpart. We find that drive amplitude - a parameterdropped in RWA - is critical for optimizing fidelity and map out high-fidelityregimes. Our results demonstrate the necessity of going beyond RWA inunderstanding how long-range gates can be realized in DQD qubits, with chargequbits offering considerable advantages in high-fidelity operation.