Digital Control of a Superconducting Qubit Using a Josephson Pulse Generator at 3 K

Scaling of quantum computers to fault-tolerant levels relies critically on the integration of energy-efficient, stable, and reproducible qubit control and readout electronics. In comparison to traditional semiconductor-control electronics (TSCE) located at room temperature, the signals generated by rf sources based on Josephson-junctions (Ms) benefit from small device sizes, low power dissipation, intrinsic calibration, superior reproducibility, and insensitivity to ambient fluctuations. Previous experiments to colocate qubits and JJ-based control electronics have resulted in quasiparticle poisoning of the qubit, degrading the coherence and lifetime of the qubit. In this paper, we digitally control a 0.01-K transmon qubit with pulses from a Josephson pulse generator (JPG) located at the 3-K stage of a dilution refrigerator. We directly compare the qubit lifetime T-1, the coherence time T-2*, and the thermal occupation P-th when the qubit is controlled by the JPG circuit versus the TSCE setup. We find agreement to within the daily fluctuations of +/- 0.5 mu s and +/- 2 mu s for T-1 and T-2, respectively, and agreement to within the 1% error for P-th. Additionally, we perform randomized benchmarking to measure an average JPG gate error of 2.1 x 10(-2). In combination with a small device size (< 25 mm(2)) and low on-chip power dissipation (<< 100 mu W), these results are an important step toward demonstrating the viability of using JJ-based control electronics located at temperature stages higher than the mixing-chamber stage in highly scaled superconducting quantum information systems.