Quantum precision measurement is based on the basic principle of quantum mechanics by using the interaction between light, atoms and magnetism to measure physical quantities, also known as precision measurements based on microscopic particle systems and their quantum states. As an important means of quantum precision measurement, interferometer precision measurement technology has great application value in quantum communication. The linear interferometer measures the magnitude of the physical quantity by using the phase change obtained from the measurements, but measurement accuracy is limited and unable to meet the requirements of today's scientific problems for the precision measurement of some physical quantities. On this basis, nonlinear interferometer is able to take advantage of the quantum entangled state, that is, using the two light fields of quantum correlation characteristics to realize quantum enhanced precision measurement, thus greatly improving the measurement sensitivity, Therefore, the scope of application is wider, but the preparation of quantum entangled states has many limitations in practical manipulation. With the maturity of experimental conditions and technology, how to use both of these interferometers to further improve the measurement accuracy of the phase signal so as to break the limitation to shot noise, breaking the standard quantum limit and even approaching to the Heisenberg limit has become a frontier research topic . In this paper, we introduce several methods to improve the accuracy of parameter evaluation in the measurement process by using linear (including an atomic/photon interferometer) and nonlinear interferometer to call quantum resources at different stages. High-precision measurement can be achieved by inputting non-classical states into the interferometer, such as compressed state, bi-fock state, and NOON state. And we also introduce the weak measurement developed for the direct observation of quantum states and its application to non-Hermitian systems, and the multiparameter measurement proposed to eliminate the accuracy balance between parameters. Compared with the first two measurement methods, weak measurement method is based on the weak value amplification principle of an indirect measurement. Measurements are performed virtually without perturbing the quantum system, which does not lead the wave function to collapse, the weak value of the real and virtual part have different physical significance, The combination of weak measurement theory and non-Hermitian system also further improves the measurement sensitivity. Multi-parameter measurement uses quantum entanglement, quantum control and other quantum resources to make the measurement progress reach the Heisenberg limit, which is the current research hotspot in the field of precision measurement. Furthermore, we present a conjecture whether there will be multi-atomic mixing measurements based on atomic spin effects or ultra-high sensitivity measurement instruments with precision of fT or even aT by using other particles detection. Finally, several measurement methods are analyzed and compared with each other, and the development prospect of quantum precision measurement is forecasted.
Quantum precision measurement is based on the basic principle of quantum mechanics by using the interaction between light, atoms and magnetism to measure physical quantities, also known as precision measurements based on microscopic particle systems and their quantum states. As an important means of quantum precision measurement, interferometer precision measurement technology has great application value in quantum communication. The linear interferometer measures the magnitude of the physical quantity by using the phase change obtained from the measurements, but measurement accuracy is limited and unable to meet the requirements of today's scientific problems for the precision measurement of some physical quantities. On this basis, nonlinear interferometer is able to take advantage of the quantum entangled state, that is, using the two light fields of quantum correlation characteristics to realize quantum enhanced precision measurement, thus greatly improving the measurement sensitivity, Therefore, the scope of application is wider, but the preparation of quantum entangled states has many limitations in practical manipulation. With the maturity of experimental conditions and technology, how to use both of these interferometers to further improve the measurement accuracy of the phase signal so as to break the limitation to shot noise, breaking the standard quantum limit and even approaching to the Heisenberg limit has become a frontier research topic . In this paper, we introduce several methods to improve the accuracy of parameter evaluation in the measurement process by using linear (including an atomic/photon interferometer) and nonlinear interferometer to call quantum resources at different stages. High-precision measurement can be achieved by inputting non-classical states into the interferometer, such as compressed state, bi-fock state, and NOON state. And we also introduce the weak measurement developed for the direct observation of quantum states and its application to non-Hermitian systems, and the multiparameter measurement proposed to eliminate the accuracy balance between parameters. Compared with the first two measurement methods, weak measurement method is based on the weak value amplification principle of an indirect measurement. Measurements are performed virtually without perturbing the quantum system, which does not lead the wave function to collapse, the weak value of the real and virtual part have different physical significance, The combination of weak measurement theory and non-Hermitian system also further improves the measurement sensitivity. Multi-parameter measurement uses quantum entanglement, quantum control and other quantum resources to make the measurement progress reach the Heisenberg limit, which is the current research hotspot in the field of precision measurement. Furthermore, we present a conjecture whether there will be multi-atomic mixing measurements based on atomic spin effects or ultra-high sensitivity measurement instruments with precision of fT or even aT by using other particles detection. Finally, several measurement methods are analyzed and compared with each other, and the development prospect of quantum precision measurement is forecasted.
The measurement of physical quantities and measurement units standard promote the development of metrology. Especially, the developments of laser interference and atomic frequency standard bring a revolutionary leap for metrology. Many precision measurement techniques have been proposed and experimentally demonstrated, such as gravitational wave measurements and laser gyroscopes based on laser interferometry, and atomic clocks and atomic gyroscopes based on the atom interferometry. Recently, a new branch of science, quantum metrology, has grown up to further explore and exploit the quantum techniques for precision measurement of physical quantities.#br#This paper will focus on recent developments in quantum metrology and interference based on coherence and correlation of light and atom. Firstly, we briefly review the development of metrology. Then, we introduce our own researches in recent years, including quantum-correlation SU(1,1) optical interferometer based on four wave mixing process in atomic vapor and the atom-light hybrid interferometer based on Raman scattering in atomic vapor.#br#Interferometer is a powerful tool to measure physical quantities sensitive to the inference wave with high precision, and has been widely used in scientific research, industry test, navigation and guidance system. For example, the laser interferometer is able to measure optical phase sensitive quantities, including length, angular velocity, gravitational wave and so on. Meanwhile, the atom interferometer is sensitive to the change of atomic phase caused by the light, gravity, electric and magnetic fields. As a new type of interferometry, the atom-light hybrid interferometer, is sensitive to both the optical phase and atomic phase. Furthermore, SU(1,1) interferometer and nonlinear atom-light hybrid interferometer have the ability to beat the standard quantum limit of phase sensitivity. Quantum interference technology, whose phase measurement accuracy can break through the limit of standard quantum limit, is the core of quantum metrology and quantum measurement technology.
High-sensitivity interferometers are one of the basic tools for precision measurement, and their sensitivity is limited by their shot noise limit (SNL), which is determined by vacuum fluctuations of the probe field. The quantum interferometer with novel structures can break the SNL and measure the weak signals, such as the direct observation of gravity wave signal. Combining classical interferometers and the optical parametric amplifier (OPA) can enhance the signal; meanwhile, the quantum noise is kept at the vacuum level, so that the sensitivity of the nonlinear interferometer beyond the SNL can be achieved. By analyzing in detail the influence of system parameters on the precision of quantum metrology, including the intensity of optical fields for phase sensing, the gain factor of OPA, and the losses inside and outside the interferometers, the application conditions of high-sensitivity nonlinear quantum interferometers are obtained. Quantum interferometer-based OPAs provide the direct references for the practical development of quantum precise measurement.
Quantum computing can transform the field of highly-precise measurement systems in the physical sciences with new levels of sensitivity, resolution, and capability to compute data. Quantum-enhanced measurement systems may also reach levels of precision that are constrained by the inherent quantum noise due to quantum superposition, entanglement and coherence. This opens up to innovations in such research as magnetic field sensing, atomic clock synchronization, and seeing gravitational waves. Quantum computing can be used to retrieve high-fidelity information in noisy data, improvements in signal-to-noise ratios by quantum techniques, like phase estimation and the Quantum Fourier Transform, are possible, and quantum techniques have been demonstrated to surpass classical limits. Moreover, quantum sensors that are integrated into quantum computing structures make real-time feedback and adaptive measurement methods feasible, dynamically optimising system efficiency. Moreover, quantity metrology combined with quantum computing enables sensitive studies in fundamental physics, including experimental tests of quantum gravity or a study of the dark matter. Current developments in error correction and hardware design are rapidly enhancing the usefulness of quantum systems in practice, even in the face of the current technological challenges of qubit decoherence and scalability. This paper discusses the current state of quantum computing in the field of precision measurement and potential future directions, the way that quantum computing might transform the physical sciences and push the boundaries of experimental accuracy.
Michelson interferometer can be applied to not only the building block of the fundamental research of physics, but also the precise measurement, such as the direct observation of gravity wave signal. Therefore, high performance Michelson interferometer is the key step towards the implementation of direct observation of weak gravity wave signal. Recently, the vacuum noise was reduced by injecting squeezed vacuum into the unused port of Michelson interferomter, and the phase signal optical field in Mach-Zender interferometer is amplified based on the four-wave mixing in hot Rubidium atom. Here we study high sensitivity quantum Michelson interferometer. In the Michelson interferometer, the linear optical beam splitter is replaced by a non-degenerated optical parametric amplifier to realize the splitting and combining of optical fields, and the squeezed vacuum is also injected into the unused port of interferomter, so that the high signal-to-noise ratio and high sensitivity of phase measurement can be realized. Due to the inevitable optical losses, the losses inside and outside the Michelson interferometer are considered in our theoretical model. We investigate the influences of the losses inside and outside the Michelson interferometer on the sensitivity of phase measurement. By theoretical calculation, we analyze the dependence of sensitivity of phase measurement on system parameters, such as intensity of optical fields for phase sensing, gain factor of non-degenerated optical parametric amplifier, the losses inside and outside the Michelson interferometer, and the squeezing parameter of input squeezed vacuum, and thus the condition of high sensitivity nonlinear Michelson interferometer can be obtained. In a broad system parametric range, the quantum Michaleson interferometer can surpass standard quantum limit, and the nonlinear Michaleson interferometer with squeezed state injection can provide the optimal sensitivity for phase measurement. The nonlinear Michelson interferometer with squeezed state is suitable for weak signal measurement. While the gain factor of non-degenerated optical parametric amplifier is large enough, the nonlinear Michelson interferometer without injecting the squeezed vacuum can still reach the optimal sensitivity, which reduces the use of quantum resources. When the phase sensing optical field is strong, the linear Michelson interferometer with injecting the squeezed vacuum can also reach the optimal sensitivity, and the sensitivity is robust for both losses inside and outside the interferometer. All the kinds of interferometers are more sensitive to the loss inside the interferometer than outside the interferometer, and the sensitivity of phase measurement can be improved by reducing the loss inside the interferometer. Our result provides direct reference of experimental implementation of high performance interferometer for high precision quantum metrology.
The ability to manipulate light has allowed scientists to verify fundamental theories of physics and to develop a new generation of technologies that use photons as a primary resource. Recent developments in quantum measurement theory have offered new alternatives to approach some of the most remarkable problems in quantum physics. Consequently, the principles of quantum mechanics have been exploited in the development of quantum technologies such as optical metrology, quantum communication, and quantum information. In recent years, weak measurements and two of its most remarkable variants: weak value amplification and direct measurement, have been developed and are considered important resources for quantum applications. In this paper, we discuss weak measurements and some significant applications of weak values. We elaborate on how distinct forms of weak values are used to observe and amplify small effects or to directly measure the quantum wave function of photons, a crucial task for schemes for quantum communication and quantum information. We also review some of the most recent methods for weak value amplification and direct measurement that our group has developed.
Precision measurement plays a vital role in metrology. To achieve the ultimate precision predicted by quantum theory, one can leverage quantum entanglement—correlations between particles of light or matter that cannot be explained in classical physics. The use of quantum entanglement in probing an object enhances measurement precision by a factor of √N beyond what is attainable with classical resources, where precision is typically limited by Poisson noise. Here, N represents the number of entangled particles. To date, most research efforts have focused on understanding and characterizing non-classical correlations between two particles. For instance, in 2022, optical clocks were synchronized using quantum entanglement, achieving frequency uncertainties of √2 lower than what is possible with non-entangled clocks. However, despite rapid advancements in single-particle sensing technologies, the generation and characterization of quantum correlation involving three or more particles remain an ongoing challenge. The absence of rigorous measurement standards for multi-particle entanglement, coupled with the lack of photon-number-resolving (PNR) detection capabilities, can lead to faulty measurements and reduced metrological accuracy and precision. It is therefore essential to establish robust methodologies and standards for the creation and validation of multi-particle entanglement to enable quantum-limited precision measurements. These developments will provide significant impacts in various fields, including optical astronomy, frequency standards, microscopy, and secure communication. The integration of entanglement-assisted sensors with PNR detection will enhance imaging resolution in applications such as astronomy and biological sample analysis. Additionally, standardized metrological frameworks for quantum entanglement and hardware evaluation will enhance the security level of quantum communication by mitigating vulnerabilities associated with inconsistencies arising from the use of dissimilar characterization methodologies. These fundamental research efforts will have far-reaching implications, not only improving the quality of quantum measurements but also guiding national metrology institutes in developing standardized quantum measurement protocols.