Precision measurements of spin interactions with high density atomic vapors (original) (raw)

Ultrahigh sensitivity magnetic field and magnetization measurements with an atomic magnetometer

2010

We describe an ultrasensitive atomic magnetometer based on optically pumped potassium atoms operating in a spin-exchange relaxation free regime. We demonstrate magnetic field sensitivity of 160 aT/ Hz 1/2 in a gradiometer arrangement with a measurement volume of 0.45 cm 3 and energy resolution per unit bandwidth of 44ប. As an example of an application enabled by such a magnetometer, we describe measurements of weak remnant rock magnetization as a function of temperature with a sensitivity on the order of 10 −10 emu/ cm 3 / Hz 1/2 and temperatures up to 420°C.

Liquid-State Nuclear Spin Comagnetometers

Physical Review Letters, 2012

We discuss nuclear spin comagnetometers based on ultra-low-field nuclear magnetic resonance in mixtures of miscible solvents, each rich in a different nuclear spin. In one version thereof, Larmor precession of protons and 19 F nuclei in a mixture of thermally polarized pentane and hexafluorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fluctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5 × 10 −9 Hz, or about 5 × 10 −11 Hz in ≈ 1 day of integration. In a second version, spin precession of protons and 129 Xe nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed.

In situ magnetometry for experiments with atomic quantum gases

The Review of scientific instruments, 2018

Precise control of magnetic fields is a frequent challenge encountered in experiments with atomic quantum gases. Here we present a simple method for performing in situ monitoring of magnetic fields that can readily be implemented in any quantum-gas apparatus in which a dedicated field-stabilization approach is not feasible. The method, which works by sampling several Rabi resonances between magnetically field sensitive internal states that are not otherwise used in a given experiment, can be integrated with standard measurement sequences at arbitrary fields. For a condensate of 87Rb atoms, we demonstrate the reconstruction of Gauss-level bias fields with an accuracy of tens of microgauss and with millisecond time resolution. We test the performance of the method using measurements of slow resonant Rabi oscillations on a magnetic-field sensitive transition and give an example for its use in experiments with state-selective optical potentials.

Spin-exchange-relaxation-free magnetometry with Cs vapor

2008

We describe a Cs atomic magnetometer operating in the spin-exchange relaxation-free (SERF) regime. With a vapor cell temperature of 103 • C we achieve intrinsic magnetic resonance widths ∆B = 17 µG corresponding to an electron spin-relaxation rate of 300 s −1 when the spin-exchange rate is ΓSE = 14000 s −1. We also observe an interesting narrowing effect due to diffusion. Signalto-noise measurements yield a sensitivity of about 400 pG/ √ Hz. Based on photon shot noise, we project a sensitivity of 40 pG/ √ Hz. A theoretical optimization of the magnetometer indicates sensitivities on the order of 2 pG/ √ Hz should be achievable in a 1 cm 3 volume. Because Cs has a higher saturated vapor pressure than other alkali metals, SERF magnetometers using Cs atoms are particularly attractive in applications requiring lower temperatures.

Low-noise high-density alkali-metal scalar magnetometer

Physical Review A, 2009

We present an experimental and theoretical study of a scalar atomic magnetometer using an oscillating field-driven Zeeman resonance in a high-density optically-pumped potassium vapor. We describe an experimental implementation of an atomic gradiometer with a noise level below 10 fT Hz −1/2 , fractional field sensitivity below 10 −9 Hz −1/2 , and an active measurement volume of about 1.5 cm 3. We show that the fundamental field sensitivity of a scalar magnetometer is determined by the rate of alkali-metal spin-exchange collisions even though the resonance linewidth can be made much smaller than the spin-exchange rate by pumping most atoms into a stretched spin state.

Magnetometry with entangled atomic samples

Physical Review A, 2005

We present a theory for the estimation of a scalar or a vector magnetic field by its influence on an ensemble of trapped spin-polarized atoms. The atoms interact off resonantly with a continuous laser field, and the measurement of the polarization rotation of the probe light, induced by the dispersive atom-light coupling, leads to spin squeezing of the atomic sample

High Frequency Atomic Magnetometer by Use of Electromagnetically Induced Transparency

Physical Review Letters, 2006

Atomic magnetometers have achieved magnetic sensitivities in the subfemtotesla regime. Their bandwidth is determined by the transverse spin relaxation rate, 1=T 2 , which also determines the magnetic sensitivity. It is theoretically demonstrated that by using an electromagnetically induced transparent probe beam in a pump-probe atomic magnetometer, it is possible to operate the latter at frequencies much higher than its bandwidth, maintaining a high signal-to-noise ratio.

An optically modulated zero-field atomic magnetometer with suppressed spin-exchange broadening

Review of Scientific Instruments, 2014

We demonstrate an optically pumped 87Rb magnetometer in a microfabricated vapor cell based on a zero-field dispersive resonance generated by optical modulation of the 87Rb ground state energy levels. The magnetometer is operated in the spin-exchange relaxation-free regime where high magnetic field sensitivities can be achieved. This device can be useful in applications requiring array-based magnetometers where radio frequency magnetic fields can induce cross-talk among adjacent sensors or affect the source of the magnetic field being measured.

Quantum-Enhanced Magnetometry at Optimal Number Density

Physical Review Letters

We study the use of squeezed probe light and evasion of measurement back-action to enhance the sensitivity and measurement bandwidth of an optically-pumped magnetometer (OPM) at sensitivityoptimal atom number density. By experimental observation, and in agreement with quantum noise modeling, a spin-exchange-limited OPM probed with off-resonance laser light is shown to have an optimal sensitivity determined by density-dependent quantum noise contributions. Application of squeezed probe light boosts the OPM sensitivity beyond this laser-light optimum, allowing the OPM to achieve sensitivities that it cannot reach with coherent-state probing at any density. The observed quantum sensitivity enhancement at optimal number density is enabled by measurement back-action evasion.

Subpicotesla atomic magnetometry with a microfabricated vapour cell

Nature Photonics, 2007

Highly sensitive magnetometers capable of measuring magnetic fields below 1 pT have an impact on areas as diverse as geophysical surveying 1 , the detection of unexploded ordinance 2 , space science 3 , nuclear magnetic resonance 4,5 , health care 6 and perimeter and remote monitoring. Recently, it has been shown that laboratory optical magnetometers 7,8 , based on the precession of the spins of alkali atoms in the vapour phase, could achieve sensitivities in the femtotesla range, comparable to 9-12 , or even exceeding 13 , those of superconducting quantum interference devices 6 . We demonstrate here an atomic magnetometer based on a millimetre-scale microfabricated alkali vapour cell with sensitivity below 70 fT Hz 21/2 . Additionally, we use a simplified optical configuration that requires only a single low-power laser. This result suggests that millimetre-scale, low-power femtotesla magnetometers are feasible, and we support this proposition with a simple sensitivity scaling analysis. Such an instrument would greatly expand the range of applications in which atomic magnetometers could be used.