In this work, we theoretically proposed and experimentally demonstrated the enhanced effect of prior curvature precondition on temperature sensing in a quantum-enhanced sensing system, which is constructed by combining an all-fiber two-mode squeezed light source and a Sagnac loop. By choosing the prior optimum length and curvature of polarization-maintaining fiber inside the Sagnac loop, both signal-to-noise ratio (SNR) and sensitivity can be effectively enhanced. The experimental results are summarized as follows. SNR is enhanced by the factor of 0.38 dB under balanced measurement condition. Under unbalanced measurement condition, the enhanced factors with regard to sensing depth are 0.22 and 2.34 dB for the classical double-channel light source and two-mode squeezed light source, respectively. With the support of curvature precondition, the sensing depth of the former one 15.62 dB is enhanced to 31.49 dB of the latter one by an enhanced factor of 15.87 dB, which is larger than 13.75 dB in the absence of curvature precondition, this enhanced effect still exists in the temperature sensitivity (0.982 dB/°C <1.134 dB/°C) and SNR (0.54 dB <1.7 dB). These results confirm the potential prospects of using the cross effects from other physical quantities to enhance temperature sensing in a quantum-enhanced sensing system.
In this work, we theoretically proposed and experimentally demonstrated the enhanced effect of prior curvature precondition on temperature sensing in a quantum-enhanced sensing system, which is constructed by combining an all-fiber two-mode squeezed light source and a Sagnac loop. By choosing the prior optimum length and curvature of polarization-maintaining fiber inside the Sagnac loop, both signal-to-noise ratio (SNR) and sensitivity can be effectively enhanced. The experimental results are summarized as follows. SNR is enhanced by the factor of 0.38 dB under balanced measurement condition. Under unbalanced measurement condition, the enhanced factors with regard to sensing depth are 0.22 and 2.34 dB for the classical double-channel light source and two-mode squeezed light source, respectively. With the support of curvature precondition, the sensing depth of the former one 15.62 dB is enhanced to 31.49 dB of the latter one by an enhanced factor of 15.87 dB, which is larger than 13.75 dB in the absence of curvature precondition, this enhanced effect still exists in the temperature sensitivity (0.982 dB/°C <1.134 dB/°C) and SNR (0.54 dB <1.7 dB). These results confirm the potential prospects of using the cross effects from other physical quantities to enhance temperature sensing in a quantum-enhanced sensing system.
In this work, the combination of an all-fiber two-mode squeezed state light source and Sagnac interferometer for the experimental realization of a quantum-enhanced strain and curvature sensor is presented here. The former can offer intensity-correlated twin beams, whose intensity difference noise is beyond standard quantum limit. The latter can be prepared by splicing a polarization-maintaining fiber between two standard single-mode fibers. Using the intensity interrogation method tracing the intensity variation of the sensing signal beam, we can obtain the following quantum-enhanced experimental results. In the strain sensing, signal-to-noise ratio (SNR) is enhanced by a maximal factor of 1.54 dB compared with the corresponding classical strategy under balanced measurement condition. Under unbalanced measurement condition, SNR and the sensitivity are enhanced by the maximal factors of 1.39 dB and 0.026 dB/μϵ respectively compared with the corresponding classical counterpart. In the curvature sensing, balanced measurement condition can offer a maximal factor of 1.31 dB SNR enhancement, unbalanced measurement condition will bring the maximal factors of 1.36 dB and 3.31 dB/m−1respectively enhancement in SNR and sensitivity. These results demonstrate the feasibility of the combination of all-fiber non-classical light source and various fiber-based structures as the strain and curvature sensors for many applications that demands sub-poissonian precise measurements.
A quantum-enhanced fiber curvature sensor based on single-mode fiber (SMF) taper exploiting intensity-correlated pulse twin beams has been proposed and experimentally realized. The curvature can be measured by intensity difference noise power and degree of intensity difference squeezing which are tailored by the bending-induced loss of one beam’s SMF taper. In addition, the three different waist diameters of SMF tapers, i. e.,52.12μm,61.68μm, and 67.54μmrespectively have been prepared using a fusion splicer. Finally, the maximum measured sensitivity enhancement of 4.42 dB/m−1and signal-to-noise ratio enhancement of 2.0 dB have been experimentally implemented through intensity difference measurement technique compared with the corresponding classical counterpart (double-channel light source). In contrast to other curvature sensors, this proposal has the advantages of high sensitivity, ease of fabrication, simple structure, and low cost.
The injection of squeezed light can be used to improve the sensitivity of an interferometer beyond the limit imposed by the zero-point fluctuation of the electromagnetic field. Here, we report on the realization of such a quantum-enhanced interferometer with a fiber-based Sagnac topology. Continuous wave squeezed states at 1550 nm with a noise reduction of 6.4 dB below shot noise were produced by type I optical parametric amplification and subsequently injected into the dark port of the interferometer. A reduction of the interferometer shot noise by 4.5 dB was observed, and the enhancement of the signal-to-noise ratio for a phase modulation signal generated within the interferometer could be demonstrated. We achieved a 95% fiber transmission for the squeezed states, which suggests that corresponding fiber-based quantum metrology and communication systems are feasible.
To overcome the precision limitation imposed by classical common noise and standard quantum limit (SQL) in traditional classical sensing, a single-multi-single-mode (SMS) fiber optic sensor based on the combination of self-imaging principle and two-mode squeezed light source is proposed and experimentally demonstrated. The SMS sensor is constructed by fusing a multi-mode fiber in between two single-mode fiber segments. By utilizing an intensity-correlated twin beam source (signal and idler), the signal beam acts as the sensing probe interacting with the SMS sensor, while the idler beam serves as a reference to implement balanced differential measurement. The experimental results explicitly demonstrate a maximum signal-to-noise ratio enhancement of 1.196±0.012 dB and 1.194±0.019 dB for strain sensing (0 με to 2077.9 με) and temperature sensing (30°C to 110°C), respectively. These findings confirm the sensor's capability for real-time, high-precision sub-Poissonian measurements, particularly for practical applications in electromagnetic-immune and the requirements of simultaneous discrimination of temperature and strain.
We present a simple and robust design for a squeezing-enhanced Sagnac interferometer that significantly surpasses the the shot-noise limit of sensitivity in rotational sensing. By strategically placing an optical parametric amplifier (OPA) inside the Sagnac loop, light is automatically squeezed in both forward and backward directions of the loop, which enhances the detectability of a small phase. For measuring the squeezed quadrature, we explore two approaches: parametric homodyne and direct detection. In direct detection, the intensity of the output dark port is measured directly, which is very simple, but necessitates photo-detectors of near-unit efficiency. With parametric homodyne, an additional OPA is placed at the Sagnac output to amplify the quadrature of interest above the classical noise limit, eliminating the need for near-ideal photo-detectors. Our analysis demonstrates super-classical sensitivity under most realistic conditions of loss and detector inefficiency, thereby leveraging leveraging the resources of squeezing and the principles of SU(1,1) interference, while maintaining compatibility with standard Sagnac configurations.
This research focuses on advanced noise suppression technologies for high-precision measurement systems, particularly addressing the limitations of classical noise reducing approaches. The noise level of laser sources is a crucial factor that directly affects the measurement sensitivity in applications such as gravitational wave detection and biomedical imaging. Classical feedback control technologies are effective but often encounter a bottleneck resulting from the classical noise suppression limits. To cope with these challenges, a novel method integrating quantum squeezed light with classical feedback control systems to reduce intensity noise is proposed in this work. By employing an amplitude-squeezed light field, a quantum-enhanced feedback control model is developed, thereby theoretically examining the influence of both the feedback loop gain and the degree of squeezing on the noise suppression performance. The results show that the injection of squeezed light significantly reduces the intensity noise, approaching the shot noise limit (SNL), thereby improving the system sensitivity beyond the classical noise reduction boundaries. Specifically, –10 dB squeezed state injection into the feedback system yields an additional noise suppression of approximately 8.97 dB, exceeding what is achievable using classical feedback alone. This demonstrates that the potential of the proposed method can enhance measurement precision close to the quantum noise limits without increasing the laser power. The analysis highlights the asymmetric noise suppression effects between the inner feedback loop and outer feedback loop. Although the outer loop benefits significantly from the squeezed light injection and achieves noise levels that are unattainable by classical feedback methods, the inner loop shows relatively minor improvements. This asymmetry is attributed to the inherent characteristics of quantum squeezing and the limitations of the feedback loop design. Further investigation into the individual noise components reveals that the primary contributors to the intensity noise include input noise, photodetector noise, and beam splitter-induced vacuum fluctuations. The injection of squeezed light effectively mitigates these vacuum fluctuations, which are typically a major noise source in high-precision laser systems. Theoretical research results show that the use of squeezed light in feedback control systems can effectively enhance noise suppression, equivalent to a nine fold increase in detected optical power, without the physical drawbacks of increasing laser power such as thermal noise. In conclusion, this study provides a theoretical validation of combining quantum squeezed states with classical feedback control to exceed classical noise suppression limits. The integration of a –10 dB squeezed state demonstrates a significant noise reduction, showing that this hybrid approach could revolutionize noise management in precision measurement applications. The results pave the way for further exploring quantum-enhanced control technologies in fields such as gravitational wave detection, quantum communication, and advanced optical sensing, providing a pathway for improving sensitivity and noise suppression without increasing additional power requirements.