Characterization of a near-quantum limited JTWPA in the sub GHz range

We report the gain characteristics and noise temperature results of a near-quantum-limited Josephson traveling-wave parametric amplifier (JTWPA) designed and verified to operate in the sub-GHz range of frequencies suitable for spin-based qubit platforms. We find the amplifier to be typically capable of $>20$~dB in an rf-matched environment with a bandwidth of 200~MHz about a dispersion feature centred at 775~MHz. The amplifier is found to have a near quantum limited intrinsic noise temperature of 50~mK with an achievable system noise temperature of order 200~mK. We examine the noise performance of the amplifier with the addition of multiple signal tones to emulate typical readout multiplexing in a quantum readout chain. We find that the performance of the amplifier does not degrade while simulatanousely amplifying mutliple signal frequencies and continues to operate in a near quantum lmited regime.