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arXiv · 2011.00914

Beyond the standard quantum limit of parametric amplification

M. Renger·S. Pogorzalek·Q. Chen·Y. Nojiri·K. Inomata·Y. Nakamura·M. Partanen·A. Marx·R. Gross·F. Deppe·K. G. Fedorov
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Abstract

The low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of $0.5$, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of 1 can be reached. Experimentally, we find a quantum efficiency of $0.69 \pm 0.02$, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.

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M. Renger, S. Pogorzalek, Q. Chen, Y. Nojiri, K. Inomata, Y. Nakamura, M. Partanen, A. Marx, R. Gross, F. Deppe, K. G. Fedorov. 2020-11-02. Beyond the standard quantum limit of parametric amplification. https://arxiv.org/abs/2011.00914

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