Enhanced Quantum Sensing with Dual Probing Twin Beams

Quantum metrology with light utilizes the reduced noise properties of quantum states of light for enhancing the sensitivity of measurements beyond the shot noise. The ability to take full advantage of available quantum resources is still an open question and requires customizing the response of the sensing devices. We show that a dual probing approach where both beams of a two-mode squeezed state (twin beams) of light interface with the sensing device can enhance its sensitivity beyond approaches where one beam is used as a probe and the other as a reference for intensity difference measurements. To implement this sensing configuration, we design plasmonic structures that consist of an array of nanoholes that exhibit resonances with relative shift for two orthogonal linearly polarized fields. Our calculations show that if we interface orthogonally polarized twin beams with structures that exhibit a response with opposite slopes for the different polarizations, the sensitivity in detection of local changes in refractive index approaches the sensitivity limit that can be achieved with single mode squeezed light. Although single mode quantum states, in principle, are optimal states for sensing, our approach enables the use of differential detection techniques that cancel technical noise that can limit or prevent a quantum enhancement. Finally, we present our preliminary experimental progress on this sensing approach.