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

## TL;DR

This paper demonstrates that using twin-mode quantum states of light in surface plasmon resonance sensors can significantly enhance measurement precision by reducing quantum noise through non-classical correlations.

## Contribution

It introduces a novel quantum-enhanced SPR sensing scheme utilizing twin-mode quantum states to improve refractive index estimation accuracy.

## Key findings

- Quantum noise reduction achieved via non-classical photon correlations.
- Enhanced sensitivity in refractive index measurement.
- Potential for improved biochemical and medical sensing applications.

## 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.