Magnetic Fields

Jin‐Ming Liu, Pengfei Yu, Ji-Guang Cai +1 more

We investigate the thermal entanglement of a two-qubit anisotropic Heisenberg XYZ model with both uniform and nonuniform magnetic fields in the x-z plane at thermal equilibrium. For the uniform magnetic field case, it is shown that the value of the critical magnetic field B(subscript c) may be broadened by changing the direction of the magnetic field and that the revival of entanglement is due to the combined influence of the magnetic field and the Heisenberg model's partial anisotropy in the plane which is perpendicular to the magnetic field. Moreover, the direction of the magnetic field will have an effect on the critical temperature T(subscript c) only when the field strength is large enough. For the nonuniform magnetic field case it is found that, for any direction of the magnetic field, the introduction of inhomogeneity in the magnetic field always broadens the critical magnetic field B(subscript c), but diminishes the maximum entanglement.

Ravinder Rupchand Puri

R. Mark Wilson

Hong Zhang, Sheng Zou, Xiyuan Chen

The SERF atomic spin magnetometer, which can be used to measure the residual weak magnetic field in the magnetic shield due to its ultrahigh sensitivity, is elaborated in this paper. The method of using the SERF atomic spin magnetometer to measure the residual weak magnetic field in the magnetic shield was presented. The compensating coils, which were placed inside the magnetic shield, produced the uniform magnetic fields along the x, y and z directions, and they were reverse direction with the residual weak magnetic fields; via the cross modulation method, the residual weak magnetic fields could be counteracted. At this time, the magnetic fields producing by the compensating coils were equal to the residual weak magnetic fields in the magnetic shield. The experimental results showed that the residual weak magnetic fields were approximate 0.5 nT, 1.0 nT and 7.0 nT along the x, y and z directions, respectively; and the maximum measurement errors were approximate 0.0169, 0.0377, and 0.5071 along the x, y and z directions, respectively. Finally, the reasons of measurement error were analyzed.

Emilio d’Emilio, Luigi E. Picasso

Ziting Chen, Kin To Wong, Bojeong Seo +6 more

Accurately measuring magnetic fields is essential for magnetic-field sensitive experiments in areas like atomic, molecular, and optical physics, condensed matter experiments, and other areas. However, since many experiments are often conducted in an isolated environment that is inaccessible to experimentalists, it can be challenging to accurately determine the magnetic field at the target location. Here, we propose an efficient method for detecting magnetic fields with the assistance of an artificial neural network (NN). Instead of measuring the magnetic field directly at the desired location, we detect fields at several surrounding positions, and a trained NN can accurately predict the magnetic field at the target location. After training, we achieve a below 0.3% relative prediction error of magnetic field magnitude at the center of the vacuum chamber, and successfully apply this method to our erbium quantum gas apparatus for accurate calibration of magnetic field and long-term monitoring of environmental stray magnetic field. The demonstrated approach significantly simplifies the process of determining magnetic fields in isolated environments and can be applied to various research fields across a wide range of magnetic field magnitudes.