TMTT2024PulsedLNA

Large-scale qubit readout in quantum computing

systems requires highly sensitive amplification with minimal

power consumption to reduce thermal load and preserve qubit

integrity. We propose a pulse-operated cryogenic low-noise am-

plifier (LNA) scheme that minimizes the influence from the LNA

on qubit operation and reduces power consumption by duty

cycling. A modified commercially available cryogenic hybrid LNA

based on InP HEMTs has been characterized to demonstrate the

feasibility of pulsed operation for qubit readout. The transient

noise and gain performance of the LNA was obtained through a

cryogenic time-domain noise measurement setup with 5 ns time

resolution and a measured noise standard deviation below 0.3 K.

The time-domain noise and gain performance of the LNA in

response to a square gate voltage waveform was investigated.

Through an analysis of the LNA’s recovery limitations, we

developed a fast recovery bias strategy leading to the optimization

of the gate voltage waveform using a genetic algorithm. This

resulted in strong enhancement of transient noise and gain perfor-

mance with a recovery time of 35 ns. The drain current transients

were measured to calculate the average power consumption of

the pulse-operated LNA, which confirmed a reduction in average

power consumption proportional to the duty cycle. This work

contributes to the development of high-performance and low-

power amplifier solutions critical for large-scale qubit readout

applications.