The fundamental noise limit of a phase-preserving amplifier at frequency is the standard quantum limit . In the microwave range, the best candidates have been amplifiers based on superconducting quantum interference devices (reaching the noise temperature at 700 MHz), and non-degenerate parametric amplifiers (reaching noise levels close to the quantum limit at 8 GHz). We introduce a new type of an amplifier based on the negative resistance of a selectively damped Josephson junction. Noise performance of our amplifier is limited by mixing of quantum noise from Josephson oscillation regime down to the signal frequency. Measurements yield nearly quantum-limited operation, at 2.8 GHz, owing to self-organization of the working point. Simulations describe the characteristics of our device well and indicate potential for wide bandwidth operation.
- quantum limit