A C-band cryogenic gallium arsenide low-noise amplifier for quantum applications

Large-scale superconducting quantum computers require massive numbers of high-performance cryogenic low-noise amplifiers (cryo-LNAs) for qubit readout. Here we presented a C-band monolithic microwave integrated circuit (MMIC) cryo-LNA for this purpose. This cryo-LNA is based on a 150 nm gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process and implemented with a three-stage cascaded architecture, where the first stage adopts careful impedance matching to optimize the noise and return loss. The integration of negative feedback loops adopted in the second and third stages enhances the overall stability. Moreover, the pHEMT self-bias and current multiplexing circuitry structure facilitate the reduction of power consumption and require only a single bias line. Operating at an ambient temperature of 3.6 K and consuming 15 mW, the cryo-LNA demonstrates good performance in the C-band, reaching a minimum noise temperature of 4 K and an average gain of 40 dB. We further benchmarked this cryo-LNA with superconducting qubits, achieving an average single-shot dispersive readout fidelity of 98.3% without assistance from a quantum-limited parametric amplifier. The development of GaAs cryo-LNA diversifies technical support necessary for large-scale quantum applications.