We experimentally demonstrate practical quantum enhancements to several ubiquitous sensors, including ultra-trace quantum plasmonic sensors with state of the art quantum noise levels well below the photon shot noise limit.
The ultimate sensitivity of any optically based measurement using classical resources (for example, laser or thermal light) is constrained by the photon shot noise limit (SNL). However, quantum states of light, in which photon pairs have quantum correlations or entanglement, off er a path beyond this limit. In particular, “squeezing” in these quantum states makes it possible to lower the noise in the detection system below the SNL. This can signifi cantly enhance the sensitivity of real-world devices and could thus revolutionize optical-based sensing applications
Optical sensors have applications in a range of settings, from measuring mechanical vibrations in manufacturing processes to biometrics in security devices and the detection of proteins and viruses in biomedical research. Many sensing approaches exist and plasmonic systems in particular have been studied extensively due to their ability to confine light below the diffraction limit, which greatly enhances their sensitivity compared to conventional approaches. Recently, various quantum techniques have been discovered that can outperform classical sensing ones and provide sensitivity beyond the shot-noise limit. The use of these quantum techniques in plasmonics for improving sensing performance is currently being explored. We study the performance of a plasmonic sensor that exploits the quantum nature of light and its highly confined field. We consider specialized quantum states and by comparison we show how each can provide improved sensitivity beyond the shot-noise limit.