Qubit Control Using Cryogenic Frequency Multiplication

This paper introduces a subharmonic qubit drive technique, intended to provide a method to control higher frequency superconducting qubits. This is achieved by up-converting the frequency of qubit control pulses using a superconducting frequency multiplier device after the pulses have entered the dilution refrigerator. The effectiveness of the subharmonic drive technique was evaluated against the typical direct drive approach (without frequency conversion) using a 4.83 GHz transmon qubit by measuring the error-per-gate in the two cases using randomized benchmarking. The error rates of the subharmonic drive technique and typical direct drive are equivalent when the control pulse is wider than 25 ns; the subharmonic error rate is 2.4x that of the direct drive technique when using the shortest 10 ns control pulses.