Phase-Sensitive Cascade Quantum Amplifier with Nearly Noiseless Operation

Phase-sensitive parametric devices facilitate quadrature-selective amplification with the possibility for sub-quantum-limited noise performance. In this work, we investigate the operation of a SQUID-based Josephson parametric amplifier (JPA), comparing its gain and noise performance in the phase-preserving and phase-sensitive regimes. The device, fabricated using VTT SWAPS technology, is driven in a three-wave mixing configuration and characterized in a reflection-based measurement setup at millikelvin temperatures. To directly probe the noise performance at low JPA gains, we employ a cascaded amplification scheme in which a traveling-wave parametric amplifier (TWPA) provides low-noise preamplification of the JPA output. In a phase-preserving operation, the JPA exhibits near-quantum-limited performance with a system noise temperature of 351± 53 351 ± 53 mK at 6 GHz. In contrast, phase-sensitive operation yields a minimum system noise temperature of 94± 12 94 ± 12 mK, well below the standard quantum limit of 288 mK. Our results demonstrate that a JPA–TWPA amplifier cascade opens the door to direct, high-fidelity probing of quantum devices without the need for background noise subtraction.