Directional Josephson traveling-wave parametric amplifier via non-Hermitian topology

Low-noise microwave amplifiers are crucial for detecting weak signals in quantum technologies and radio astronomy. Building an ideal device is challenging as it must amplify a broad range of frequencies while adding minimal noise. The amplification must also be directional so that it favors the observer's direction while protecting the source from its environment. Here, we introduce a fundamentally new type of superconducting Josephson traveling-wave parametric amplifier that fulfills all these requirements by exploiting non-Hermitian topological effects and time-reversal symmetry breaking via the phase of the four-wave-mixing pump. In the topological amplification phase, the device acquires an unprecedented performance such as a gain growing exponentially with system size and largely surpassing 20 dB, exponential suppression of back-wards noise below -30 dB, a bandwidth of GHz, and topological protection against disorder. This opens the door for integrating near-ideal and compact pre-amplifiers on the same chip as quantum processors.