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.
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.
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.
In this work, a sandwich fiber structure based on the combination of Talbot effect and intensity correlated twin beams has been theoretically proposed and experimentally demonstrated. The twin beams are composed of signal and idler beams. In this sense, signal beam is acted as the sensing role to interact with this sandwich fiber structure, and idler beam is regard as a reference role to implement balanced differential measurement for eliminating classical common noise and beating standard quantum limit (SQL). Comparing with SQL, the present experimental results affirm that the maximum signal-to-noise ratio enhancement of 1.196 dB in the strain sensing (0 με to 2077.9 με).
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.
We have experimentally proposed and implemented a fiber bending sensor with quantum-enhanced signal-to-noise ratio (SNR), which stems from the combination of single-mode fiber (SMF) taper and intensity correlated pulse twin beams. One beam from pulse twin beams is coupled into the SMF taper to obtain a bending-induced loss, while the other beam is also attenuated correspondingly by a variable optical attenuator to ensure maximum noise cancellation. Along this line, intensity-difference noise power between pulse twin beams is always reduced below standard quantum limit (SQL), and thus a higher SNR value compared with the corresponding double-channel light source can be realized. In this work, the three different SMF tapers with the waist diameters of85.1μm,74.9μm, and67.3μm, respectively have been prepared by a fusion splicer. The experimental results show that in the bending range of 0–20 m−1, the SMF taper with67.3μmwaist diameter shows the highest sensitivity of 0.105 dB/m−1, the resolution of 0.095 m−1, and its SNR value is enhanced by a maximal factor of 2.84 dB compared with the corresponding classical counterpart. The present bending proposal may find potential applications in monitoring the bending deformation of building structure, roadbed settlement, medical and health, etc.
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.
Quantum metrology leverages quantum resources to surpass classical limits in measurement sensitivity, enabling new capabilities across fields ranging from fundamental physics to sensing, imaging, and navigation. As these techniques mature, an increasing emphasis is being placed on translating quantum-enhanced performance into practical, robust systems that can operate outside controlled laboratory environments. The overarching objective of the work presented in this dissertation is to develop sensing platforms that achieve improved performance by leveraging quantum resources in realistic, noisy environments. In particular, this work focuses on the use of squeezed states of light, and investigates how two-mode squeezed states generated through four-wave mixing can be developed into compact sources and integrated with practical fiber-optic and plasmonic sensing platforms. Squeezed states of light, and in particular two-mode squeezed states (twin beams), constitute a powerful resource in quantum metrology. Their reduced quantum noise enables measurements below the noise level that can be achieved with classical resources, know as the shot-noise limit, offering genuine quantum advantages in precision sensing and measurement. Beyond their fundamental interest, such states provide a pathway toward practical quantum technologies capable of outperforming classical approaches in real-world applications. For many practical implementations, it is therefore highly advantageous to demonstrate squeezed light sources that are compact, stable, and compatible with existing photonic infrastructures. This is needed to lower the barrier to incorporate quantum resources into experiments and sensing platforms, particularly in environments where bulky or delicate optical setups are impractical. To demonstrate a pathway toward practical quantum sensing with squeezed light, this dissertation presents experimental studies spanning both the development of deployable squeezed-light sources and their application in practical or real-world sensing platforms. We present the development of a compact, narrowband, fiber-coupled source of squeezed light based on four-wave mixing in hot Rb 85 vapor. The system achieves more than 4 dB of intensity-difference squeezing after propagation through polarization-maintaining fibers, demonstrating that strong quantum correlations can be preserved even when fiber coupled. This platform serves as a standalone proof-of-principle demonstration of a deployable, low–size, weight, and power (low-SWaP) squeezed-light source that is well suited for applications where fiber delivery of quantum-correlated light can be readily integrated into existing experimental and sensing platforms. In addition to this source development, the dissertation investigates two distinct applications of twin-beam for quantum-enhanced sensing. The first one focuses on fiber Bragg grating (FBG) sensors, which are widely used to monitor strain, vibration, and temperature in applications ranging from civil infrastructure and aerospace systems to oil and gas pipeline monitoring. By coupling the squeezed light into separate FBGs and employing differential detection, common-mode noise is suppressed while localized perturbations are retained. This work provides a feasibility study for using twin-beams to enhance the sensitivity of FBG-based sensors beyond classical limits while providing robustness against environmental noise. The second application examines plasmonic sensors based on surface plasmon resonances in metallic nanostructures, which enable highly sensitive detection of small changes in refractive index. Such plasmonic sensors are particularly useful for applications in chemical and biological sensing, environmental monitoring, and lab-on-chip platforms, where compactness and high sensitivity to refractive index changes are critical. A dual-probing scheme is introduced in which both beams of a two-mode squeezed state interact with a polarization-dependent plasmonic nanostructure. By exploiting opposite spectral response for orthogonal polarizations, this approach improves measurement sensitivity relative to our previous technique of using one beam to probe the plasmonic sensor and the other to serve as a reference. This new technique takes advantage of transducing information into both the beams while preserving the benefits of differential detection for noise cancellation. Taken together, these studies illustrate complementary approaches for leveraging quantum correlations for practical sensing problems. Through the development of a compact, fiber-compatible squeezed-light source and independent demonstrations of enhanced performance in both fiber-optic and plasmonic sensors, this dissertation advances pathways for translating quantum sensing approaches based on quantum states of light from laboratory demonstrations into deployable metrology tools.