This work presents a cryogenic broadband three-stage cascode low-noise amplifier (LNA) in Samsung 28 nm CMOS for quantum computing. The micro-strip line conductivity was characterized at 4 K, and staggered tuning was applied to achieve flat gain and broad bandwidth. Moreover, self-resonant frequencies (SRFs) of the bypass capacitors were intentionally set at the low-frequency and high-frequency edges of the bandwidth to achieve broadband stability. Operating from 4 to 8 GHz, the LNA achieves 39.1 dB gain at 6.9 GHz, 6.8 GHz, 3-dB bandwidth, and an average 0.45-dB noise figure (NF) at 4 K. This represents the widest reported 3-dB bandwidth among cryogenic CMOS LNAs.