Quantum-enhanced plasmonic sensing

Quantum resources can enhance the sensitivity of a device beyond the classical shot noise limit and, as a result, revolutionize the field of metrology through the development of quantum-enhanced sensors. In particular, plasmonic sensors, which are widely used in biological and chemical sensing applications, offer a unique opportunity to bring such an enhancement to real-life devices. Here, we use bright entangled twin beams to enhance the sensitivity of a plasmonic sensor used to measure local changes in the refractive index. We demonstrate a 56% quantum enhancement in the sensitivity of a state-of-the-art plasmonic sensor when compared with the corresponding classical configuration and a 24% quantum enhancement when compared to an optimal single-beam classical configuration. We measure sensitivities on the order of 10(-10) RIU/ root Hz, nearly 5 orders of magnitude better than previous proof-of-principle implementations of quantum-enhanced plasmonic sensors. These results promise significant enhancements in ultratrace label-free plasmonic sensing and will find their way into areas ranging from biomedical applications to chemical detection. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement