ИСТИНА

Single Josephson junction (JJ) can be used as a microwave on-chip source for clocking digital RSFQ circuits and for qubit control. By embedding the JJ in an external microwave circuit, constant voltage steps appear on the current-voltage characteristic of the Josephson junction at the corresponding resonant frequencies and it is possible to significantly narrow the linewidth of the radiation. In this study we show the designs of an on-chip Josephson generators based on both lumped and long JJs. A spiral resonator was chosen as an external resonant microwave circuit for a lumped junction, since it allows the entire system to fit on an area of up to 1x1 mm2, and also possesses high impedance. We show that our device generates an output microwave signal with a frequency of 6.7 GHz and a linewidth of 480 kHz, with a peak output power of 10 pW. We also demonstrate DC measurements of a long JJ microwave source, which shows the possibility of generating an output signal near 5-7 GHz.