Search

Atomic magnetometers are emerging as the most sensitive sensors for magnetic field detections, and have found applications in various fields. In nuclear magnetic resonance gyroscopes (NMRG), researchers usually use an embedded atomic magnetometer to sense the transverse magnetic fields generated by the precessing nuclear spins. The additional spin-exchange and spin-destruction collisions between alkali-metal and inert gas atoms reduce the coherence time τ of the alkali-metal atom spins. In addition, in order to achieve an NMRG of high sensitivity, a relatively small bias magnetic field needs to be applied, thus giving a low Larmor frequency ω0 of the alkali-metal atom spins. These two factors violate the condition. In this paper, we systematically study the performance of this embedded atomic magnetometer when the product ζ = ω0τ is on the order of unity. We demonstrate that the sensitivity of the magnetometer depends on two dimensionless parameters ζ and the modulation depth η when the system is on resonance. We then find the key factor for achieving the best sensitivity of the magnetometer is to choose an optimized η value. As an application of our results, we consider the demodulation phase in NMRG, where the Larmor frequency of the nuclear spins is to be determined by the magnetometer. We give an analytical expression of the demodulation phase, with which one can obtain maximal nuclear magnetic resonance signals. [ABSTRACT FROM AUTHOR]

Nuclear spin fluctuation suppression is a key issue in preserving electron coherence for quantum information/computation. We propose an efficient way of nuclear spin cooling in semiconductor quantum dots (QDs) by the coherent population trapping (CPT) and the electric dipole spin resonance (EDSR) induced by optical fields and ac electric fields. The EDSR can enhance the spin flip-flop rate and may bring out bistability under certain conditions. By tuning the optical fields, we can avoid the EDSR induced bistability and obtain highly polarized nuclear spin state, which results in long electron coherence time. With the help of CPT and EDSR, an enhancement of 1500 times of the electron coherence time can been obtained after a 500 ns preparation time. [ABSTRACT FROM AUTHOR]

We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic elds. A strong spin-polarized current can be obtained by changing the dc magnetic field. It is mainly due to the resonant tunnelling. But for the ferromagnetic right electrode, the electron spin resonance also plays an important role in transport. We show that the double quantum dots with three-level mixing under crossed dc and ac magnetic fields can act not only as a bipolar spin filter but also as a spin inverter under suitable conditions. [ABSTRACT FROM AUTHOR]

An atomic magnetometer is an ultra-high-sensitivity sensor that measures magnetic fields by means of atomic spin polarization. The spatial frequency response (SFR), which describes the spin polarizations corresponding to the field at different spatial frequencies, is an important property of atomic magnetometers. To characterize the SFR, one must generate a spatially varying field with scannable spatial frequencies (in units of mm − 1 ), a concept that is similar to that in the time domain. However, it is much more difficult to generate a varying magnetic field spatially using traditional magnetic coils than it is to do so temporally. We generate an equivalent field B y sin ⁡ (ξ x) with spatial frequency ξ from 0.14 mm − 1 to 36.5 mm − 1 by modulating the pump laser beam with a digital micromirror device and then obtain the SFR of a Cs atomic magnetometer by measuring the spin polarization of Cs at different spatial frequencies. The experimentally obtained SFR agrees well with the response calculated based on the Bloch equations and Fick's second diffusion law. We also discuss a new definition of spatial resolution that can be used to characterize and compare the background spatial resolutions of different atomic magnetometers. [ABSTRACT FROM AUTHOR]

Accurate rotation sensors are highly demanded in both industrial applications and academic research. We experimentally demonstrate an angle measurement method based on an alkali-metal vapor cell. In our experiment, the rotation signal is converted to the polarization of the laser beam passing through a quarter-wave plate coaxially mounted on a detected object. The polarization is then measured by monitoring the transmission of the laser beam through the vapor cell. Using this method, we demonstrate an angle measurement sensitivity of 2 × 10 − 5 ° / Hz without a magnetic shield. The results shown in this paper provide a prototype of the angle measurement with high accuracy, compactness, and low cost. [ABSTRACT FROM AUTHOR]

The diffusion crosstalk free distance is an important parameter for spin images in atomic vapor cells and is also regarded as a limit on the spatial resolution. However, by modulating the pumping light both spatially and temporally using a digital micromirror device, a spin image of a vapor cell has been obtained with a distinguishable stripe width of 13.7 μ m, which is much smaller than the corresponding diffusion crosstalk free distance of ∼ 138 μ m. The fundamental limit on the spatial resolution as determined by diffusion and the uncertainty principle is analyzed. [ABSTRACT FROM AUTHOR]