Faraday-rotation fluctuation spectroscopy with static and oscillating magnetic fields

Under negative feedback, the quality factor Q of a radio-frequency magnetometer can be decreased by more than two orders of magnitude, so that any initial perturbation of the polarized spin system can be rapidly damped, preparing the magnetometer for detection of the desired signal. We find that noise is also suppressed under such spin-damping, with a characteristic spectral response corresponding to the type of noise; therefore magnetic, photon-shot, and spin-projection noise can be measured distinctly. While the suppression of resonant photon-shot noise implies the closed-loop production of polarization-squeezed light, the suppression of resonant spin-projection noise does not imply spin-squeezing, rather simply the broadening of the noise spectrum with Q.Furthermore, the application of spin-damping during phase-sensitive detection suppresses both signal and noise in such a way as to increase the sensitivity bandwidth. We demonstrate a three-fold increase in the magnetometer's bandwidth while maintaining 0.3 fT/ √ Hz

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“…This agrees with quantum mechanical expression of Ref. [36] derived for a spin-1/2 particle. While it is clear from Eq.…”

Section: Equation 18 Implies That Ssupporting

confidence: 91%

“…As described by Ref. [36], the spin projection noise associated with measurement of S x can be calculated by…”

Section: B Spin-projection Noisementioning

confidence: 99%

Spin damping in an rf atomic magnetometer

2013

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“…The fundamental source of noise is due to the quantum projection of each spin along the transverse directions causing a transverse magnetization of the sample [42,54]. This noise can be decreased by using larger sample volumes.…”

Section: Noise Sourcesmentioning

confidence: 99%

“…The model of Ref. [54] is an approximation to the noise in a real material. But the parametric features of this model, such as the noise peak at the Larmor frequency with a bandwidth set by T 2 and its dependence on sample volume, are expected to be realized in a real material [42].…”

Section: Magnetization Noisementioning

confidence: 99%

Proposal for a Cosmic Axion Spin Precession Experiment (CASPEr)

et al. 2014

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We propose an experiment to search for QCD axion and axionlike-particle dark matter. Nuclei that are interacting with the background axion dark matter acquire time-varying CP-odd nuclear moments such as an electric dipole moment. In analogy with nuclear magnetic resonance, these moments cause precession of nuclear spins in a material sample in the presence of an electric field. Precision magnetometry can be used to search for such precession. An initial phase of this experiment could cover many orders of magnitude in axionlike-particle parameter space beyond the current astrophysical and laboratory limits. And with established techniques, the proposed experimental scheme has sensitivity to QCD axion masses m a ≲ 10 −9 eV, corresponding to theoretically well-motivated axion decay constants f a ≳ 10 16 GeV. With further improvements, this experiment could ultimately cover the entire range of masses m a ≲ μ eV, complementary to cavity searches.

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“…Hence hole contribution is always centered at ω = 0 while the electron spin precession peak follows the electron Larmor frequency. [43][44][45] This is illustrated in Fig. 4, where the numerically calculated spin noise spectrum is presented and the transformation of the single peak at zero magnetic field to the two-peak structure is seen.…”

Section: Resultsmentioning

confidence: 90%

Exciton spin noise in quantum wells

Smirnov¹,

Glazov²

2014

Phys. Rev. B

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A theory of spin fluctuations of excitons in quantum wells in the presence of non-resonant excitation has been developed. Both bright and dark excitonic states have been taken into account. The effect of a magnetic field applied in a quantum well plane has been analyzed in detail. We demonstrate that in relatively small fields the spin noise spectrum consists of a single peak centered at a zero frequency while an increase of magnetic field results in the formation of the second peak in the spectrum owing to an interplay of the Larmor effect of the magnetic field and the exchange interaction between electrons and holes forming excitons. Experimental possibilities to observe the exciton spin noise are discussed, particularly, by means of ultrafast spin noise spectroscopy. We show that the fluctuation spectra contain, in addition to individual contributions of electrons and holes, an information about correlation of their spins.

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Faraday-rotation fluctuation spectroscopy with static and oscillating magnetic fields

Cited by 31 publications

References 34 publications

Spin damping in an rf atomic magnetometer

Spin damping in an rf atomic magnetometer

Proposal for a Cosmic Axion Spin Precession Experiment (CASPEr)

Exciton spin noise in quantum wells

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