Physicists develop mass-produced photonic sensors that work at the quantum limit for high-precision monitoring of the environment, cancer, and more

 　　In contemporary society, sensors are found in many fields such as safety and environmental monitoring, medical care, and autonomous driving, and play a key role in recording important information in social life.

　　Quantum sensing promises to dramatically improve the performance of existing sensors, enabling them to measure physical quantities more accurately and quickly, and will have a transformative impact on many fields of science and technology.

　　Recently, a team of physicists led by the University of Bristol in the United Kingdom announced that they have demonstrated that "using a ring resonator, it is possible to make high-precision measurements of important physical properties without the need for complex optical quantum states and detection schemes". It is understood that the ring resonator can be mass-manufactured using current semiconductor processes, and is expected to be practically used in environmental monitoring, ultrasound imaging, antibody profiling, and cancer detection.

　　The theoretical and practical application of quantum information science is one of the most exciting research activities in the field of science and technology today.

　　"Quantum states of light have been shown to improve the accuracy of absorption estimates over classical strategies," said the researchers. "But most current quantum sensing schemes rely on special entangled or squeezed states of light and substances that are difficult to generate and detect," said the researchers. This is a major obstacle to the full utilization and practical deployment of quantum-limited sensor capabilities."

　　Currently, the detection and characterization of analytes using optical ring resonators has been applied in a wide range of scenarios, such as gas sensing, measurement of mechanical strain, and biochemical analysis. However, the fundamental limits of using these structures to estimate analyte properties in quantum metrology have hardly been specifically investigated.

　　Quantum metrology attempts to determine and reach the fundamental quantum limit (the limit of measurement accuracy at the quantum scale) for estimating physical parameters, primarily to identify quantum strategies that outperform classical sensing schemes on an equivalent set of resources, e.g., given a probe photon The average number of nonclassical states is used to improve phase and absorption accuracy estimation in various applications such as interferometry, magnetometry, and spectroscopy.

　　One goal of this study is to quantify whether engineered photonic circuits with classical light sources can outperform non-classical state probes in a standard single-pass scheme. Compared with single-pass strategies, resonant optical cavities expand the prospects for improved precision due to the enhanced light intensity and the increased number of interactions.

　　It is understood that the system used by the researchers is an all-pass ring resonator coupled by a ring resonator, which greatly improves the interaction of light with the sample.

　　The researchers quantified the magnitude of these precision gains when the analytes rapidly coupled to the all-pass ring resonator changed the absorption coefficient and refractive index, and using quantum estimation theory, determined that the single-mode Gaussian probe state yielded the highest possible precision experimental parameters.

　　At the optimal operating point, they found that the use of strongly squeezed states has no advantage over coherent state probes, and that coherent state probes in all-pass ring resonator systems are quantum-wise better than single-pass strategy probes.

　　The results show that engineering photonic circuits is a promising technique for improving the accuracy of parameter estimation. "Using this technique to sense changes in the absorption coefficient or refractive index can be used to identify and characterize a variety of materials and biochemical samples," the researchers mentioned

　　. "We are one step closer to all integrated photonic sensors operating at the detection limit dictated by quantum mechanics," Bellsley said.

　　It is understood that the Quantum Engineering Technology Laboratory was established in 2015 and currently has a team from the University of Bristol in Physics and Electrical Engineering. With over a hundred researchers in the School of Electrical Engineering, working to accelerate the application of quantum technologies and develop new functions and hardware that use quantum phenomena, including "quantum computing hardware, quantum communications, new ways to enhance sensing and imaging, and research New Platforms for Fundamental Quantum Physics, etc.". Its goal is to bring quantum scientific discoveries out of the lab and serve society by collaborating with some of the world's best quantum start-ups.

　　A key enabling technology platform for the lab is integrated quantum photonics, which has transformed quantum experiments around the world to a certain extent. Integrated quantum photonics uses photonic integrated circuits to control the quantum states of light, providing a promising approach for the miniaturization and scale-up of optical quantum circuits, which can be applied to quantum computing, quantum communication, quantum simulation, and more.