Digital bit pattern based control of transmon qubits

Classical programmable superconducting logic near the QPU could be beneficial for scaling quantum computers to large-scale error corrected systems. However, the associated cooling budget dramatically limits the complexity of practically implementable circuits and thus in comparison to traditional analog driving, one could benefit considerably from simpler purely digital methods.

Towards such ends, we've investigated driving of qubits with bit patterns generated at 25 Gbps using digital room temperature electronics. We've performed randomized benchmarking using an FPGA and a D flip-flop as a single bit DAC outputting nontrivial bit patterns. We observe 99.8% single qubit gate fidelity for 50 ns gates.

The benefits of digital driving are not necessarily limited to just cryogenic electronics as considerable cost savings and perhaps even some fidelity improvements may be realizable in comparison to analog electronics with this method. Due to flip-flop based reclocking, timing jitter and noise floor are reduced even in comparison to most analog systems.