Quantum-enhanced measurements can provide information about the properties of a physical system with sensitivities beyond what is fundamentally possible with conventional technologies. However, this advantage can be achieved only if quantum measurement technologies are robust against losses and real-world imperfections, and can operate in regimes compatible with existing systems. Here, we demonstrate a quantum receiver for coherent communication, the performance of which not only surpasses the standard quantum limit, but does so for input powers extending to high mean photon numbers. This receiver uses adaptive measurements and photon number resolution to achieve high sensitivity and robustness against imperfections, and ultimately shows the greatest advantage over the standard quantum limit ever achieved by any quantum receiver at power levels compatible with state-of-the-art optical communication systems. Our demonstration shows that quantum measurements can provide real and practical advantages over conventional technologies for optical communications.
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The authors acknowledge financial support from the Physics Frontier Center at the Joint Quantum Institute. F.E.B. thanks J. Kosloski and J. Goldhar for discussions. The authors also thank S.V. Polyakov, who developed the original FPGA-based platform on which our data acquisition system was built45.
The authors declare no competing financial interests.
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Becerra, F., Fan, J. & Migdall, A. Photon number resolution enables quantum receiver for realistic coherent optical communications. Nature Photon 9, 48–53 (2015). https://doi.org/10.1038/nphoton.2014.280
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