The S^p_q equivalent current system of the quiet day geomagnetic variation in the polar region is very complicated. It is composed of several currents, such as the ionospheric dynamo current and the auroral electrojet...The S^p_q equivalent current system of the quiet day geomagnetic variation in the polar region is very complicated. It is composed of several currents, such as the ionospheric dynamo current and the auroral electrojet caused by the field aligned current. S p q is unsymmetrical in both polar regions. In this paper, the S p q current systems are analyzed in the corrected geomagnetic coordinates (CGM) instead of the conventional geomagnetic coordinates (GM), and the symmetries of the S p q current in different systems are compared. Then the causes of S p q asymmetry in the GM coordinates are discussed; the effects of each component in S p q are determined.展开更多
Acceleration sensing, an essential branch of quantum sensing, faces a fundamental trade-off between resolution and bandwidth. Here, we present a quantum-enhanced optomechanical accelerometer(QEOMA), simultaneously ach...Acceleration sensing, an essential branch of quantum sensing, faces a fundamental trade-off between resolution and bandwidth. Here, we present a quantum-enhanced optomechanical accelerometer(QEOMA), simultaneously achieving the improvement of the sensing resolution and bandwidth in contrast with a classical counterpart.By tailoring quantum squeezed light, the optomechanical cooperativity is significantly raised, extending the sensing bandwidth. Quantum squeezed light increases the equivalent Q value of the optomechanical accelerometer owing to the reduction of the mechanical damping rate, driving the resolution improvement at the resonance frequency. At off-resonance frequencies, the resolution improvement is attributed to the imprecision noise reduction. We obtain the measured noise power spectrum and inferred acceleration resolution for the(3,3),(4,4),(5,5), and(6,6) mechanical modes, respectively. The maximum quantum enhancement is measured for the(6,6) mechanical mode with a 38.4% resolution enhancement and 1.55-fold bandwidth broadening in contrast with a coherent probe. The proposed QEOMA shows significant potential for applications ranging from ultralight dark matter searches to inertial navigation of fast-moving objects.展开更多
文摘The S^p_q equivalent current system of the quiet day geomagnetic variation in the polar region is very complicated. It is composed of several currents, such as the ionospheric dynamo current and the auroral electrojet caused by the field aligned current. S p q is unsymmetrical in both polar regions. In this paper, the S p q current systems are analyzed in the corrected geomagnetic coordinates (CGM) instead of the conventional geomagnetic coordinates (GM), and the symmetries of the S p q current in different systems are compared. Then the causes of S p q asymmetry in the GM coordinates are discussed; the effects of each component in S p q are determined.
基金National Natural Science Foundation of China(62225504,12274275,62027821,U22A6003,62375162,12304399,12174234)Key R&D Program of Shanxi(202302150101004).
文摘Acceleration sensing, an essential branch of quantum sensing, faces a fundamental trade-off between resolution and bandwidth. Here, we present a quantum-enhanced optomechanical accelerometer(QEOMA), simultaneously achieving the improvement of the sensing resolution and bandwidth in contrast with a classical counterpart.By tailoring quantum squeezed light, the optomechanical cooperativity is significantly raised, extending the sensing bandwidth. Quantum squeezed light increases the equivalent Q value of the optomechanical accelerometer owing to the reduction of the mechanical damping rate, driving the resolution improvement at the resonance frequency. At off-resonance frequencies, the resolution improvement is attributed to the imprecision noise reduction. We obtain the measured noise power spectrum and inferred acceleration resolution for the(3,3),(4,4),(5,5), and(6,6) mechanical modes, respectively. The maximum quantum enhancement is measured for the(6,6) mechanical mode with a 38.4% resolution enhancement and 1.55-fold bandwidth broadening in contrast with a coherent probe. The proposed QEOMA shows significant potential for applications ranging from ultralight dark matter searches to inertial navigation of fast-moving objects.
