54 research outputs found
Atomic-state diagnostics and optimization in cold-atom experiments
We report on the creation, observation and optimization of superposition
states of cold atoms. In our experiments, rubidium atoms are prepared in a
magneto-optical trap and later, after switching off the trapping fields,
Faraday rotation of a weak probe beam is used to characterize atomic states
prepared by application of appropriate light pulses and external magnetic
fields. We discuss the signatures of polarization and alignment of atomic spin
states and identify main factors responsible for deterioration of the atomic
number and their coherence and present means for their optimization, like
relaxation in the dark with the strobe probing. These results may be used for
controlled preparation of cold atom samples and in situ magnetometry of static
and transient fieldsComment: 15 pages and 9 figures (including supplementary information
Nitrogen-Vacancy Ensemble Magnetometry Based on Pump Absorption
We demonstrate magnetic field sensing using an ensemble of nitrogen-vacancy
centers by recording the variation in the pump-light absorption due to the
spin-polarization dependence of the total ground state population. Using a 532
nm pump laser, we measure the absorption of native nitrogen-vacancy centers in
a chemical vapor deposited diamond placed in a resonant optical cavity. For a
laser pump power of 0.4 W and a cavity finesse of 45, we obtain a noise floor
of 100 nT/ spanning a bandwidth up to 125 Hz. We
project a photon shot-noise-limited sensitivity of 1
pT/ by optimizing the nitrogen-vacancy concentration and
the detection method.Comment: 7 pages and 5 figure
Feasibility and resolution limits of opto-magnetic imaging of neural network activity in brain slices using color centers in diamond
We suggest a novel approach for wide-field imaging of the neural network
dynamics of brain slices that uses highly sensitivity magnetometry based
on nitrogen-vacancy (NV) centers in diamond. Invitro recordings in brain
slices is a proven method for the characterization of electrical neural
activity and has strongly contributed to our understanding of the
mechanisms that govern neural information processing. However, this
traditional approach only acquires signals from a few positions, which
severely limits its ability to characterize the dynamics of the
underlying neural networks. We suggest to extend its scope using NV
magnetometry-based imaging of the neural magnetic fields across the
slice. Employing comprehensive computational simulations and theoretical
analyses, we determine the spatiotemporal characteristics of the neural
fields and the required key performance parameters of an NV
magnetometry-based imaging setup. We investigate how the technical
parameters determine the achievable spatial resolution for an optimal 2D
reconstruction of neural currents from the measured field distributions.
Finally, we compare the imaging of neural slice activity with that of a
single planar pyramidal cell. Our results suggest that imaging of slice
activity will be possible with the upcoming generation of NV magnetic
field sensors, while single-shot imaging of planar cell activity remains
challenging
Precision temperature sensing in the presence of magnetic field noise and vice-versa using nitrogen-vacancy centers in diamond
We demonstrate a technique for precision sensing of temperature or the
magnetic field by simultaneously driving two hyperfine transitions involving
distinct electronic states of the nitrogen-vacancy center in diamond. Frequency
modulation of both driving fields is used with either the same or opposite
phase, resulting in the immunity to fluctuations in either the magnetic field
or the temperature, respectively. In this way, a sensitivity of 1.4 nT
Hz or 430 K Hz is demonstrated. The presented technique
only requires a single frequency demodulator and enables the use of
phase-sensitive camera imaging sensors. A simple extension of the method
utilizing two demodulators allows for simultaneous, independent, and
high-bandwidth monitoring of both the magnetic field and temperature.Comment: 5 pages, 4 figure
Contributed review: camera-limits for wide-field magnetic resonance imaging with a nitrogen-vacancy spin sensor
Sensitive, real-time optical magnetometry with nitrogen-vacancy centers in diamond relies on accurate imaging of small (≪10−2), fractional fluorescence changes across the diamond sample. We discuss the limitations on magnetic field sensitivity resulting from the limited number of photoelectrons that a camera can record in a given time. Several types of camera sensors are analyzed, and the smallest measurable magnetic field change is estimated for each type. We show that most common sensors are of a limited use in such applications, while certain highly specific cameras allow achieving nanotesla-level sensitivity in 1 s of a combined exposure. Finally, we demonstrate the results obtained with a lock-in camera that paves the way for real-time, wide-field magnetometry at the nanotesla level and with a micrometer resolution
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