Two-qubit gates for superconducting QC using direct-digital synthesis*

We describe the implementation of a microwave platform for readout and control of superconducting qubits. This platform, which we name Presto, is based on a radio-frequency system-on-chip (RFSoC) and leverages direct-digital synthesis (DDS). Thanks to DDS, Presto can directly control and readout qubits in the full 4-8 GHz band without the need for external analog mixers and local oscillators, making it a scalable and cost-effective solution for quantum-technology experiments.

Presto has up to 16 output channels, all phase-coherent and synchronized to a single master clock. This synchronization, which arises naturally from DDS, enables simple implementation of complex quantum algorithms where the relative phase of different microwave tones must be controlled with great accuracy.

We discuss the main functionality of our FPGA firmware, with particular focus on the primitives for constructing complex experiment sequences. We also show characterization and calibration of two-qubit gates such as controlled-Z (CZ) and exchange-type (iSWAP).