2025/12/22 by N. Nehra, Nehra, N., N. Bourlet +17
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Mechanical and Optical Resonators #Quantum Information and Cryptography #Quantum Physics (quant-ph) #Quantum and electron transport phenomena
paper · doi:10.48550/arxiv.2512.19902
openalex publication_date 2025/12/22 · openalex created_date 2025/12/25 · openalex updated_date 2026/07/28
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.