TMTT2024PulsedLNA

Large-scale qubit readout in quantum computingsystems requires highly sensitive amplification with minimalpower consumption to reduce thermal load and preserve qubitintegrity. We propose a pulse-operated cryogenic low-noise am-plifier (LNA) scheme that minimizes the influence from the LNAon qubit operation and reduces power consumption by dutycycling. A modified commercially available cryogenic hybrid LNAbased on InP HEMTs has been characterized to demonstrate thefeasibility of pulsed operation for qubit readout. The transientnoise and gain performance of the LNA was obtained through acryogenic time-domain noise measurement setup with 5 ns timeresolution and a measured noise standard deviation below 0.3 K.The time-domain noise and gain performance of the LNA inresponse to a square gate voltage waveform was investigated.Through an analysis of the LNA’s recovery limitations, wedeveloped a fast recovery bias strategy leading to the optimizationof the gate voltage waveform using a genetic algorithm. Thisresulted in strong enhancement of transient noise and gain perfor-mance with a recovery time of 35 ns. The drain current transientswere measured to calculate the average power consumption ofthe pulse-operated LNA, which confirmed a reduction in averagepower consumption proportional to the duty cycle. This workcontributes to the development of high-performance and low-power amplifier solutions critical for large-scale qubit readoutapplications.