Quantum noise reduction in intensity-sensitive surface-plasmon-resonance sensors

Abstract

We investigate the use of twin-mode quantum states of light with symmetric statistical features in their photon number for improving intensity-sensitive surface plasmon resonance (SPR) sensors. For this purpose, one of the modes is sent into a prism setup where the Kretschmann configuration is employed as a sensing platform and the analyte to be measured influences the SPR excitation conditions. This influence modifies the output state of light that is subsequently analyzed by an intensity-difference measurement scheme. We show that quantum noise reduction is achieved not only as a result of the sub-Poissonian statistical nature of a single mode, but also as a result of the non-classical correlation of the photon number between the two modes. When combined with the high sensitivity of the SPR sensor, we show that the use of twin-mode quantum states of light notably enhances the estimation precision of the refractive index of an analyte. With this we are able to identify a clear strategy to further boost the performance of SPR sensors, which are already a mature technology in biochemical and medical sensing applications.

Probing Decoherence in Plasmonic Waveguides in the Quantum Regime

“…However, the role of pure phase damping is not completely negligible. Our work shows that both amplitude and pure phase damping can lead to decoherence in quantum plasmonic systems, and it provides useful information about the loss of coherence that should be considered when designing plasmonic waveguide systems for phase-sensitive quantum applications, such as quantum sensing [20][21][22][23] and quantum imaging [23,24]. The techniques developed here for characterising decoherence in plasmonic waveguides may be useful for studying other plasmonic nanostructures, such as those used as nanoantennas [4], as unit cells in metamaterials [63,64] and as nanotraps for cold atoms [65].…”

“…These nanophotonic devices are important for emerging quantum technologies, such as photonic-based quantum computers [16,17] and quantum communication networks [18]. Following on from early work probing SPPs with quantum states of light, such as entangled photons [19], recent studies have demonstrated several key quantum applications, including quantum sensing and imaging [20][21][22][23][24], quantum spectroscopy [25], quantum logic gates [26], entanglement generation [27] and distillation [28], and quantum random number generation [29]. What is surprising is that all of these applications can be realized even in the presence of loss, which is always present in plasmonic systems as they are scaled down to confine light to smaller scales.…”

Using states with a large photon number variance to increase quantum Fisher information in single-mode phase estimation

“…Nevertheless, the fiducial photon number distributions we introduce here would be useful for an operating regime of a parameter that is locally calibrated in advance, so the identification of minute changes of the parameter is only of interest. That is, fortunately, often the case, e.g., for plasmonic sensors [36,37] or phase tracking [38]. In such cases, the validity of the quantum Cramér-Rao bound can be investigated in terms of the required minimum number of measurements and the minimum prior knowledge of the parameter [17,18].…”

Quantum plasmonic sensing using single photons

“…For our sensor to be understood in the context of transmission spectroscopy we treat the actual reflection of a single photon from the ATR setup as a transmission through the ATR setup, as in Ref. [26]. The generation of the single-photon state (the signal) is heralded by a detection of its twin photon (the idler), due to the quantum correlation of photon pairs initially produced via spontaneous parametric down conversion (SPDC).…”