Nb/a-Si/Nb-junction Josephson-based arbitrary waveform synthesizers for quantum information
David Olaya, John Biesecker, Manuel Castellanos Beltran, Adam Sirois, Paul Dresselhaus, Samuel P. Benz, Pete Hopkins, Logan Howe
We demonstrate Josephson arbitrary waveform synthesizers (JAWS) with increased operating temperature range for temperatures below 4 K. These JAWS synthesizers were fabricated with externally-shunted Nb/a-Si/Nb junctions whose critical current exhibits improved temperature stability compared to the self-shunted Nb/Nb0.15Si0.85/Nb junctions typically used. Vertical stud resistors made of 230 nm of PdAu were developed to provide the milliohm shunt resistance required for junction overdamping while maintaining a small footprint suitable for high-density series arrays embedded in a coplanar waveguide. We evaluated the performance of these resistors from 3.8 K down to 20 mK. We designed, fabricated and tested a JAWS circuit with 4650 externally shunted Nb/a-Si/Nb JJs with a critical current density (Jc) of 0.12 mA/μm2 and critical current (Ic) of 3 mA. This circuit was designed to be mounted to the 3 K stage of a dilution refrigerator and used to control and calibrate a qubit mounted at the 10 mK stage. To increase the circuit density of the JAWS circuits we made arrays of two-junction vertical stacks. Current-voltage (I-V) curves of this JAWS circuit with stacked junctions under microwave excitation show Shapiro steps with quantum-locking ranges similar to those of JAWS circuits used for qubit control.
, Biesecker, J.
, Castellanos Beltran, M.
, Sirois, A.
, Dresselhaus, P.
, Benz, S.
, Hopkins, P.
and Howe, L.
Nb/a-Si/Nb-junction Josephson-based arbitrary waveform synthesizers for quantum information, IEEE Transactions on Applied Superconductivity, [online], https://doi.org/10.1109/TASC.2023.3249141, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935839
(Accessed September 23, 2023)