Variable Frequency Pulse Generation From Breathers in Josephson Transmission Lines

Single flux quantum technology has the potential to enhance readout and control of superconducting quantum systems due to their low energy consumption, high speed, and cryogenic operating temperatures. Current cryogenic readout and control typically requires microwave pulses of specific frequencies to travel between the room temperature control electronics and the cryogenic setup. Latency in control and readout can be improved by generating pulses within the dilution refrigerator. In this work, we consider a protocol for generating gigahertz frequency microwave tones from trains of dc-centered flux solitons and fluxoids in Josephson transmission lines using the dynamics of breather formation, without room temperature synthesis or shunt/bias resistors. Simulations show that pulses with frequencies in the range of 15.2 GHz to 21.5 GHz can be generated with maximal energy efficiency of 97% and bandwidth from 40 MHz to 365 MHz. This protocol can also be used to generate gigahertz frequency Gaussian pulses. We detail metrics relevant to the control and readout of quantum systems, such as input power, output power, and footprint.