125 Nanosecond Two-Qubit Gates Advance Quantum Control

Researchers have demonstrated two-qubit operations in 125-135 ns using a new framework for quantum control. Qi Ding and colleagues designed gates with both frequency and amplitude modulation of microwave drives, enabling systematic analysis and design without requiring qubit frequency tunability. Using Floquet theory to analyze and design these drives, numerical simulations using typical transmon qubit parameters achieved a universal gate set, including X, Hadamard, phase and CZ gates, with control error well below 0.1% and gate times of 25-40 ns for single-qubit operations and 125-135 ns for two-qubit operations.

They show an always-on CZ gate tailored for driven qubits, which has gate times of 80-90 ns. This approach offers a path to fast, high-fidelity gates in superconducting quantum processors while preserving reduced flux-noise sensitivity, and can help alleviate frequency-crowding constraints.

Frequency- and Amplitude-Modulation Enables Universal Quantum Control

1%, demonstrating high fidelity essential for complex quantum computations. This approach bypasses the need for tunable qubit frequencies by shifting the modulation to the microwave drives themselves, a design choice validated through the use of Floquet theory to analyze and design the drives.