Coherent on-chip microwave source based on a voltage-biased Josephson junction*

The control of a large quantum processor is typically implemented by channeling shaped microwave signals to the qubits operating at many different frequencies. The conventional techniques based on room temperature electronics encounters restrictions such as the latencies and power consumption.

In this work, we present a quantitative study of an on-chip coherent microwave source based on a Josephson junction strongly coupled to a mode of a superconducting resonator, both theoretically and experimentally. We demonstrate that the source can generate microwave signals with narrow linewidth (<1 Hz), low noise (<-120 dBc/Hz at 1 MHz offset frequency), relatively high output (>25 pW), and a dc-to-rf power conversion efficiency of about 15%. We confirm that the expected infidelity bound arising from the phase noise of our source in a typical quantum-logic operation is below 0.1 % up to 10-ms evolution ensuring that the signal quality is sufficient for the control of quantum systems.