Fiber Salinity Sensing Based on Single Photon Interferometer with Quantum-Limited Precision

Yun Peng, Yong Zhao

Yun Peng, Sen Qin, Siqi Zhang +1 more

Yun Peng, Conghai Ge, Jiajia Shi +1 more

Photon sensors have a lot of applications in our productive life, from inspection of steel building structures to early disease screening in preventive medicine. However, the precision of these sensors is limited by the shot-noise limit (SNL). Fortunately, previous studies have shown that quantum technology not only has better resolution than traditional sensing methods but also can achieve ultrahigh precision that breaks the SNL. Here, a new fiber salinity sensing method with quantum-limited precision is demonstrated by applying the single-photon interferometer. A novel detection method is designed and implemented by using the Fisher information analysis. Also, the precision is defined as the estimation error of the single-photon transmittance. The salinity sensitivity of the single-photon interferometer is about −0.00053/‰ with a good linearity. The salinity resolution of the proposed fiber salinity sensor is 0.062‰. Also, the detection precision is beyond the SNL. This work demonstrates that the introduction of quantum resources has opened a new door for high-performance detection technology.

Avi Zadok

Tenghui Mao, Hailong Wang, Dongxu Wang +3 more

Ruiyang Chen, Yi-Han Luo, Jinbao Long +1 more

Optical interferometers are extensively used in fundamental physics studies, gravitational wave detection, quantum metrology, topological photonics, and quantum information processing. Fiber-based interferometers are compact, mechanically robust, and cheap, and thus are ubiquitously deployed. However, the optical phase in fiber interferometers is sensitive to ambient perturbation, resulting in compromised phase-sensing precision. Therefore, phase control, shifting, and stabilization of fiber interferometers are essential. Methods to create stable interference patterns and to lock a fiber interferometer at arbitrary phase have been shown, which however are sophisticated, bulky, and delicate, preventing wider application in harsh environments outside laboratories or in space. Here we demonstrate an innovative method for arbitrary-phase locking of fiber unbalanced Mach-Zehnder interferometers. Compared with existing methods, our method is much simpler. We showcase the preparation and characterization of a narrow-band, energy-time-entangled photon state generated in integrated nonlinear microresonators, where two-photon interference visibility reaches 0.993(6). Our method constitutes a critical building block for photonic quantum networks, and is useful to emerging single-photon interference in curved space-time that facilitates exploration of the interface of quantum mechanics and general relativity.