A near–quantum-limited Josephson traveling-wave parametric amplifier

TLDR

Amplifying microwave signals with high gain over a broad frequency range is essential for solid‑state quantum information processing, yet achieving broadband operation remains challenging. The authors engineered a traveling‑wave parametric amplifier comprising a long chain of Josephson junctions. The amplifier achieved high gain across a gigahertz‑wide bandwidth and enabled high‑fidelity qubit readout, potentially allowing simultaneous measurement of up to 20 qubits to scale quantum‑information protocols. See Macklin et al., *Science*, this issue p.

Abstract

Stringing together a powerful amplifier Amplifying microwave signals with high gain and across a broad range of frequencies is crucial in solid-state quantum information processing (QIP). Achieving broadband operation is especially tricky. Macklin et al. engineered an amplifier that contains a long chain of so-called Josephson junctions (see the Perspective by Cleland). The amplifier exhibited high gain over a gigahertz-sized bandwidth and was able to perform high-fidelity qubit readout. Because the amplifier will be capable of reading out as many as 20 qubits simultaneously, it may help to scale up QIP protocols. Science , this issue p. 307 ; see also p. 280