Sensing using heralded single photons: An application towards ultra-sensitive temperature measurement

Abstract

A novel ultra-sensitive temperature sensor utilizing Heralded Single Photons (HSPs) is proposed and experimentally verified in this investigation. HSPs are crucial in various quantum technologies. The utilization of a heralded single-photon (HSP), as opposed to a classical light source, enables superior sensitivity in quantum sensing applications. This investigation focuses on the successful generating HSPs to design a highly sensitive quantum optical temperature sensor. The HSPs were produced from a PPKTP nonlinear crystal using the spontaneous parametric down-conversion process (SPDC) under the quasi-phase matching (QPM) condition. The signal and idler photons resulting from this process were transmitted through two different identical optical fibers and then to two identical single-photon detectors. The temporal properties of these photons were analyzed using a coincidence counter. A portion of the fiber carrying the signal was decladded to serve as the sensor probe. The sensor was calibrated by measuring the average transmittance with varying temperatures near the sensor probe. The sensing principle is explained deriving an expression for average transmittance as a function of temperature. The measurement error surpassed the Standard Quantum Limit (SQL), improving measurement sensitivity. The resolution and sensitivity of the developed quantum sensor were shown to be 0.0925 °C and 0.00677 /°C respectively. This study emphasizes the potential for enhancing sensitivity and minimizing shot noise with the use of HSPs. The merits of the proposed sensor, over the other quantum senor is its less complex design and low decoherence.