arXiv subjects

Michael V. Romalis

Publications and source records attributed to Michael V. Romalis.

8 recordsLinked to original sources

arXiv2025

A $^{3}$He-$^{21}$Ne Ramsey Comagnetometer with sub-nHz frequency resolution

Nuclear spin comagnetometers offer exceptional precision in measurements of spin energy levels and exhibit long-term stability, making them powerful tools for probing spin-dependent physics beyond the Standard Model as well as for inertial rotation sensing. We describe a new $^{3}$He-$^{21}$Ne Ramsey comagnetometer operating with an in-situ $^{87}$Rb magnetometer for initialization and sensing of nuclear spins. During free precession of nuclear spins we turn off all lasers and introduce a microwave field to suppress back-action from Rb atoms. We demonstrate that scalar and dipolar interactions between nuclear spins can be eliminated via control of the polarized sample geometry. These improvements result in a bias-free measurement with a frequency sensitivity of 0.6 nHz after 6 hours of integration.

physics.atom-ph↗

arXiv2025

Pulsed Dual-axis Alkali-metal-noble-gas Comagnetometer

Alkali-metal-noble-gas comagnetometers are precision probes well-suited for tests of fundamental physics and inertial rotation sensing, combining high sensitivity of the spin-exchange-relaxation free (SERF) magnetometers with inherent suppression of magnetic field noise. Past versions of the device utilizing continuous-wave optical pumping are sensitive to a single axis perpendicular to the plane spanned by the orthogonal pump and probe laser beams. These devices are susceptible to light shifts in the alkali atoms, and to power and beam pointing fluctuations of both the probe and pump lasers, the latter of which is a dominant source of $1/f$ noise. In this work, we model and implement an approach to alkali-metal-noble-gas comagnetometers using pulsed optical pumping. After each pump laser pulse, an off-resonance probe beam measures the precession of noble-gas-spins-coupled alkali spins via optical rotation in the dark, thus eliminating effects from pump laser light shift and power fluctuations. Performing non-linear fitting on the sinusoidal transient signal with a proper phase enables separate and simultaneous measurement of signals along two orthogonal axes in the plane perpendicular to the pump beam. Effects from beam pointing fluctuations of the probe beam in the pump-probe plane is fundamentally eliminated, and signal response to pump beam pointing fluctuations is suppressed by compensation from noble-gas nuclear spins.

physics.atom-ph↗

arXiv2024

Vapor cell Rydberg atom electrometry with time-separated fields

Rydberg atoms have large transition electric dipole moments and high sensitivity to electric fields. We describe a new method for microwave field sensing in a vapor cell consisting of separate excitation, quantum evolution between two Rydberg levels in the dark and state-dependent detection with probe laser transmission. Using microwave pulse techniques we study homogeneous and inhomogeneous relaxation of the coherence between Rydberg levels and demonstrate detection of a 10 GHz signal with electric field sensitivity of 10 nV/cm/Hz$^{1/2}$.

physics.atom-ph↗

arXiv2020

New limits on Anomalous Spin-Spin Interactions

We report the results of a new search for long range spin-dependent interactions using a Rb -$^{21}$Ne atomic comagnetometer and a rotatable electron spin source based on a SmCo$_{5}$ magnet with an iron flux return. By looking for signal correlations with the orientation of the spin source we set new constrains on the product of the pseudoscalar electron and neutron couplings $g^e_p g^n_p/\hbar c<1.7\times10^{-14}$ and on the product of their axial couplings $g^e_A g^n_A/\hbar c<5\times10^{-42}$ to a new particle with a mass of less than about $1~μ$eV. Our measurements improve by about 2 orders of magnitude previous constraints on such spin-dependent interactions.

physics.atom-ph↗

arXiv2019

Precision calculation of scalar nuclear spin-spin coupling in a noble gas mixture

Indirect spin-spin interactions between nuclei bound in a molecule are well-known in nuclear magnetic resonance, but such interactions between unbound atoms are less well studied and are often assumed to be zero. We present the first precision calculation of this interaction between 129Xe and 3He nuclei in a gas. Relativistic, state-of-the-art electronic structure theory is used to compute the scalar coupling constant J(R) and the interatomic potential energy function, V(R), as functions of the Xe-He internuclear distance R. Using virial expansion we find the nuclear spin enhancement factor kappa = -0.0105 +/- 0.0015 in excellent agreement with recent experiments. This interaction is particularly important for precision measurements using nuclear spin co-magnetometers.

physics.atom-ph↗

arXiv2014

New classes of systematic effects in gas spin co-magnetometers

Atomic co-magnetometers are widely used in precision measurements searching for spin interactions beyond the Standard Model. We describe a new $^3$He-$^{129}$Xe co-magnetometer probed by Rb atoms and use it to identify two general classes of systematic effects in gas co-magnetometers, one associated with diffusion in second-order magnetic field gradients and another due to temperature gradients. We also develop a general and practical approach for calculating spin relaxation and frequency shifts due to arbitrary magnetic field gradients and confirm it experimentally.

physics.atom-ph↗

arXiv2013

Laboratory search for a quintessence field

A cosmic scalar field evolving very slowly in time can account for the observed dark energy of the Universe. Unlike a cosmological constant, an evolving scalar field also has local spatial gradients due to gravity. If the scalar field has a minimal derivative coupling to electromagnetism, it will cause modifications of Maxwell's equations. In particular, in the presence of a scalar field gradient generated by Earth's gravity, regions with a magnetic field appear to be electrically charged and regions with a static electric field appear to contain electric currents. We propose experiments to detect such effects with sensitivity exceeding current limits on scalar field interactions from measurements of cosmological birefringence. If the scalar field has derivative couplings to fermions, it would also generate observable effects in precision spin precession experiments.

astro-ph.CO↗

arXiv2012

Observation of optical chemical shift by precision nuclear spin optical rotation measurements and calculations

Nuclear spin optical rotation (NSOR) is a recently developed technique for detection of nuclear magnetic resonance via rotation of light polarization, instead of the usual long-range magnetic fields. NSOR signals depend on hyperfine interactions with virtual optical excitations, giving new information about the nuclear chemical environment. We use a multi-pass optical cell to perform first precision measurements of NSOR signals for a range of organic liquids and find clear distinction between proton signals for different compounds, in agreement with our earlier predictions. Detailed first principles quantum-mechanical NSOR calculations are found to be in good agreement with the measurements.

physics.chem-ph↗