Qubit Control-Pulse Generator Circuits for Operation at Cryogenic Temperatures

Solid-state quantum bits (qubits) generally require cryogenic operating temperatures together with rapid voltage (or current) pulse generation for qubit control and readout. Conventionally this is achieved by generating the signals at 300 K, transmitting them along very long coaxial cables that span ges 4 m from 300 K to sub-K (30-500 mK) into a dilution refrigerator, and reading-out the final qubit states via similar lengths of cable. Here we fabricate the control-pulse generator circuits using a foundry-processed SOS-CMOS technology that is capable of operation down to sub-K temperatures so that control signals can be generated at cryogenic temperatures in the near vicinity of the qubits. We present two full-custom large-scale integrated (LSI) control-pulse generator circuits: (a) a mixed-mode; and (b) a digital design each comprising hundreds of devices, and show pulse characteristics at 4.2 K, demonstrating LSI circuit operation at low temperatures. The mixed-mode design showed lower power dissipation but had increasing jitter at longer dwell times. The digital design eliminated jitter but at the expense of increased power dissipation. Although power dissipation is higher in the digital design, it should be possible to thermally anchor such control circuits at the 1 K stage of a dilution refrigerator thereby minimizing heat propagation to the qubits.