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arXiv · 2512.19902

DC-powered broadband quantum-limited microwave amplifier

N. Nehra·N. Bourlet·A. H. Esmaeili·B. Monge·F. Cyrenne-Bergeron·A. Paquette·M. Arabmohammadi·A. Rogalle·Y. Lapointe·M. Hofheinz
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Abstract

Fast, high-fidelity, single-shot readout of superconducting qubits in quantum processors demands quantum-limited amplifiers to preserve the optimal signal-to-noise ratio. Typically, quantum-limited amplification is achieved with parametric down-conversion of a strong pump tone, which imposes significant hardware overhead and severely limits scalability. Here, we demonstrate the first DC-powered broadband amplifier operating within 0.2 photons of the quantum limit. Our impedance-engineered Inelastic Cooper-pair Tunneling Amplifier (ICTA)-a voltage-biased SQUID in which Cooper pairs tunnel inelastically by emitting signal-idler photon pairs-operates in reflection, delivering 13 dB of average gain across a 3.5 GHz bandwidth in a single stage. Semiclassical simulations accurately predict the gain and saturation power, enabling further design improvements. By eliminating the pump-tone infrastructure, the broadband ICTA promises to dramatically reduce the hardware complexity of quantum-limited amplification in superconducting quantum processors.

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N. Nehra, N. Bourlet, A. H. Esmaeili, B. Monge, F. Cyrenne-Bergeron, A. Paquette, M. Arabmohammadi, A. Rogalle, Y. Lapointe, M. Hofheinz. 2025-12-22. DC-powered broadband quantum-limited microwave amplifier. https://doi.org/10.1103/c4zz-pbk4

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