ABSTRACT Quantum sensors are devices that utilize quantum systems' properties to achieve high‐precision measurements of physical quantities, such as magnetic fields and temperature. The metrological precision of quantum sensors refers to their ability to provide accurate and reliable measurements with minimal uncertainty. In this paper, we propose a quantum sensor consisting of multiple atoms arranged in a spin chain, exposed to a thermal bath at a temperature and an external weak magnetic field with a magnetic‐field gradient for quantum thermometry and magnetometry. Employing the Hilbert‐Schmidt speed (HSS), a popular measure of quantum statistical speed to quantify precision limits in parameter estimation theory, we have investigated in detail how the magnetic‐field gradient and spin chain position influence the quantum sensor's metrological capabilities. We show that the performance and precision of our quantum sensor depend on the spin chain position and the magnetic field and its gradient; increasing these factors' values reduces estimation precision and weakens quantum sensor performance. Finally, increasing the number of atoms in a quantum sensing structure improves the accuracy of temperature and field estimation.
ABSTRACT Quantum sensors are devices that utilize quantum systems' properties to achieve high‐precision measurements of physical quantities, such as magnetic fields and temperature. The metrological precision of quantum sensors refers to their ability to provide accurate and reliable measurements with minimal uncertainty. In this paper, we propose a quantum sensor consisting of multiple atoms arranged in a spin chain, exposed to a thermal bath at a temperature and an external weak magnetic field with a magnetic‐field gradient for quantum thermometry and magnetometry. Employing the Hilbert‐Schmidt speed (HSS), a popular measure of quantum statistical speed to quantify precision limits in parameter estimation theory, we have investigated in detail how the magnetic‐field gradient and spin chain position influence the quantum sensor's metrological capabilities. We show that the performance and precision of our quantum sensor depend on the spin chain position and the magnetic field and its gradient; increasing these factors' values reduces estimation precision and weakens quantum sensor performance. Finally, increasing the number of atoms in a quantum sensing structure improves the accuracy of temperature and field estimation.
Abstract Quantum sensors can enable the simultaneous and precise measurement of multiple physical parameters, facilitating the development of dual-sensing techniques. In this paper, we report on the simultaneous multi-parameter quantum sensing of temperature and magnetic field based on a quantum sensor consisting of a two-qubit Heisenberg XYZ chain, which enables joint quantum thermometry and magnetometry. Qubits interact via ferromagnetic and antiferromagnetic couplings, and are in thermal equilibrium with a heat bath in the presence of an external magnetic field. Specifically, the sensor’s response to perturbations, like temperature and magnetic field changes, is analyzed through quantum Fisher information (QFI), providing a measure of the sensing precision. We investigate the effects of different types of inter-qubit couplings and external magnetic fields on the accuracy of multi-parameter estimation. Our results demonstrate that simultaneous multi-parameter estimation improves the speed of information extraction and processing, accuracy, and sensitivity of our quantum sensor. This work provides a promising avenue for developing high-performance multiparameter quantum sensors with potential applications in various fields, including materials science, biomedicine, environmental monitoring, aerospace, industrial production, and other fields.
This study examines a quantum sensor consisting of two qubits modeled in an XXZ Heisenberg spin chain under a homogeneous magnetic field, for use in quantum thermometry and magnetometry. The sensor is subjected to a common classical environment driven by static noise and is in thermal equilibrium with a heat bath. We analyze the impact of spin–spin, Dzyaloshinskii–Moriya, and Kaplan–Shekhtman–Entin-Wohlman–Aharony interactions, as well as the static noise characterized by the disorder parameter, on the sensor's time-evolved state. We also assess the influence of magnetic field homogeneity on performance. Employing quantum Fisher information criteria, we determine the sensor's metrological precision. The performance of the proposed sensor in estimating the external magnetic field and temperature in weak and strong field regimes is different over time with temperature variations. In the strong magnetic field regime, static noise reduces the sensitivity of quantum sensing, while in the weak field regime, this effect is negligible. Our sensor achieves optimal sensitivity and precision for temperature and magnetic field estimation in the presence of static noise and in the weak magnetic field and low temperature regime. Finally, we demonstrate that the quantum sensor achieves a stable sensitivity and precision in its performance over time in quantum magnetometry and thermometry, which can be very valuable in quantum sensing. Moreover, we propose some experimental platforms for the realization of our quantum sensor.
We study the performance of quantum sensors composed of four qubits arranged in different geometries for magnetometry and thermometry. The qubits interact via the transverse-field Ising model with both ferromagnetic and antiferromagnetic couplings, maintained in thermal equilibrium with a heat bath under an external magnetic field. Using quantum Fisher information, we evaluate the metrological precision of these sensors. For ferromagnetic couplings, weakly connected graphs (e.g., the chain graph, P_4) perform optimally in estimating weak magnetic fields, whereas highly connected graphs (e.g., the complete graph, K_4) excel at strong fields. Conversely, K_4 achieves the highest sensitivity for temperature estimation in the weak-field regime. In the antiferromagnetic case, we uncover a fundamental trade-off dictated by spectral degeneracy: configurations with non-degenerate energy spectra - such as the pan-like graph (three qubits in a triangle with the fourth attached) - exhibit strong magnetic field sensitivity due to their pronounced response to perturbations. In contrast, symmetric structures like the square graph, featuring degenerate energy levels (particularly ground-state degeneracy), are better suited for precise thermometry. Notably, our four-qubit sensors achieve peak precision in the low-temperature, weak-field regime. Finally, we introduce a spectral sensitivity measure that quantifies energy spectrum deformations under small perturbations, providing a simple heuristic indicator of metrological sensitivity.
Quantum precision measurement and sensing aims to obtain a measurement accuracy beyond the limits specified by classical measurement techniques and achieve ultra-high precision measurements of physical quantities, such as magnetic field, inertia, gravity, and time by employing quantum resources and effects. With the advancement of quantum optics, atomic physics, and related fields, in addition to the incentives of the Nobel Prize and the “quantization” of the seven basic physical quantities of the International Unit, precision measurement has entered the quantum era. Compared with conventional sensors based on classical technology, quantum sensors can surpass the standard quantum limit. In addition, quantum sensors are more appropriate for precision measurements because they are not affected by manufacturing differences, defects, impurities, aging, and other factors. It has broad application potential in biomagnetism, geomagnetism, space magnetic field detection, and so on. Furthermore, its practical applications include complicated systems, poor portability and operability, high power consumption, and high cost. However, many issues remain to be addressed. Given the broad application prospect of precision measurement, certain international institutions, for instance, NIST, have begun researching chip-scale atomic sensing devices. Among the reponed chip-scale atomic systems thus far, the progress of the atomic clock and magnetometer is paramount. In this paper, we review the latest development and application of chip-scale atomic clocks and magnetometers and examine their opportunities and challenges. Finally, by taking the homebuilt microfabricated atomic magnetometer as an example, we describe the mechanism of spin squeezing-assisted quantum-enhanced metrology and provide a long-term outlook for chip-scale quantum-enhanced metrology.
Recent breakthroughs in quantum technology pave the way for extensive utilization of higher-dimensional quantum systems, which outperform their qubit counterparts in terms of capabilities and versatility. We present a framework for accurately predicting weak external magnetic fields using a higher-dimensional many-body quantum probe. We demonstrate that dimension serves as a valuable resource for quantum sensing when a transverse spin-s Ising chain interacts locally with a magnetic field whose strength has to be determined. We observe the distinct performance of sensors for spin chains with half-integer and integer spins. Furthermore, we highlight that the time duration appropriate for quantum-enhanced sensing increases with the increase of dimension. Additionally, we observe that, in addition to nearest-neighbor interactions, incorporating interactions between the next nearest-neighbor sites increases sensing precision, particularly for spin chains with integer spins. We also prove the dimensional-dependence of the bound on quantum Fisher information which provides the limit on the precision in estimating parameters.
Abstract Tensor measurements play a vital role in both fundamental sciences and interdisciplinary applications such as navigation and remote sensing which require sensitive perception of the gradient of vector fields. Fundamentally, these measurements rely on the estimation of multiple parameters, which is a key focus in metrology. Quantum metrology has achieved remarkable success in surpassing the standard quantum limit for single-parameter estimation, offering extraordinary sensitivity. Quantum multiparameter estimation has also been demonstrated recently with few-particle quantum systems. Here, we develop tensor quantum metrology by advancing multiparameter quantum sensing to an unprecedented level with both high scalability and multidimensional performance, fulfilling the essential demands on sensitivity for tensor measurements. We generate a bright, multidimensional polarization-entangled light source from an atomic ensemble, with three simultaneously squeezed Stokes operators, enabling superior performance in multiparameter quantum sensing compared to conventional polarization-entangled light. By employing such a quantum light in a tensor magnetometry, we achieve a 6 dB quantum enhancement in both direction and amplitude measurements of magnetic field gradient, with a directional gradient sensitivity of 21μrad/cm/√Hz and an amplitude gradient sensitivity of 6 fT/cm/√Hz. As the first realization of high-sensitivity quantum-enhanced sensing of a tensor field, this work marks a milestone in the advancement of quantum metrology.