Designing fast, high-fidelity quantum gates for superconducting qubits

摘要

I will discuss some of our recent theoretical studies on the balance between high gate speed and high gate fidelity in superconducting circuits used as qubits. Two-qubit gate speeds are set by the strength of the interaction between the qubits. As a result, stronger interactions lead to faster gates. I will present our recent results on the minimum gate times required to implement various two-qubit and three-qubit gates in terms of the two-qubit coupling strength. I will then present the results of our studies on the effect of the weak anharmonicity in superconducting qubits on two-qubit gate fidelities. When dealing with weakly anharmonic qubits, one needs to take into account quantum states of the superconducting circuit other than the two states used as the computational basis. Stronger two-qubit coupling then leads to larger leakage outside the computational basis, thus reducing the gate fidelity. We analyze how these considerations apply to present-day superconducting qubit circuits and how one needs to balance speed and gate fidelity.