We demonstrate detection of a weak alternate-current magnetic field by application of the spinecho technique to F = 2 Bose-Einstein condensates. A magnetic field sensitivity of 12 pT/ √ Hz is attained with the atom number of 5 × 10 3 at spatial resolution of 99 µm 2 . Our observations indicate magnetic field fluctuations synchronous with the power supply line frequency. We show that this noise is greatly suppressed by application of a reverse phase magnetic field. Our technique is useful in order to create a stable magnetic field environment, which is an important requirement for atomic experiments which require a weak bias magnetic field.
Radio-frequency pulses are applied to probe and control the Larmor precession of a spin-2 Bose–Einstein condensate subject to a magnetic field gradient. Using the techniques of Ramsey interferometry and Stern–Gerlach absorption imaging, a helical spin pattern was clearly observed as spatial variations in the atomic density distribution. We experimentally show that the spin echo technique reduces the effects of spatially inhomogeneous and temporally fluctuating spin evolution, and improves the repeatability of the interferometry.
We generate spin currents in an 87 Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin coherence, as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic π pulses (bang-bang control), producing longer spin-coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.
Physical properties of filaments in Cu/HfO2/Pt conducting-bridge memory (CB-RAM) were investigated basing on direct observation by conducting atomic force microscopy (C-AFM) and energy dispersive X-ray spectroscopy (EDS), R-T characteristics until liquid nitrogen temperature, and I-V characteristics both in air and in vacuum. As a result, physical picture of filaments in Cu/HfO2/Pt structures was revealed. Filaments consist of Cu containing large residual resistance and the cross-sectional area of the filament, Sfila, was roughly proportional to set voltage, Vset, even when current compliance was kept constant. Interestingly, resistivities of filaments are same among all the filaments in different samples and are invariant even after repetitive switching that changes resistance of the filaments. Cu/HfO2/Pt obeyed the universal relation that reset current, Ireset, is proportional to the inverse of resistance in a low resistance state, 1/RLRS, which is known to be applicable to oxygen-migration-based resistive switching memories such as Pt/NiO/Pt. Considering the invariance of resistivity of the filament, this suggests the fact that Ireset is decided dominantly by Sfila. In addition, it was suggested that moisture is necessary for dissolution and migration of Cu to form filaments.
We generate spin currents in an 87 Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of twobody collisions. In addition, the spin coherence, as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic π pulses (bang-bang control), producing longer spin coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.
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